PodcastItLater: Add dark mode support

- Added theme switcher script with localStorage persistence -
Respects system dark mode preference (prefers-color-scheme) - Added
theme toggle button to HomePage and BillingPage - Uses Bootstrap 5.3
data-bs-theme attribute for dark mode - Theme persists across page
loads - Icon changes between moon (light) and sun (dark)

Task: t-64tkB5

2 files changed, 127 insertions, 22 deletions

diff --git a/.tasks/tasks.jsonl b/.tasks/tasks.jsonl
index 8fc1a5a..335b615 100644
--- a/.tasks/tasks.jsonl
+++ b/.tasks/tasks.jsonl
@@ -35,3 +35,4 @@
 {"taskCreatedAt":"2025-11-09T22:19:27.303689497Z","taskDependencies":[],"taskId":"t-1pIV0ZF","taskNamespace":"Biz/PodcastItLater.hs","taskParent":"t-143KQl2","taskStatus":"Done","taskTitle":"Implement billing page UI component with pricing and upgrade options","taskType":"WorkTask","taskUpdatedAt":"2025-11-09T23:04:20.974801117Z"}
 {"taskCreatedAt":"2025-11-09T22:38:46.235799803Z","taskDependencies":[],"taskId":"t-1qZlMb4","taskNamespace":null,"taskParent":null,"taskStatus":"Open","taskTitle":"Add a 'task show <id>' command that prints out a long, easy to read (for humans) version of the task. Include dependencies and all information fields in the output","taskType":"WorkTask","taskUpdatedAt":"2025-11-09T22:38:46.235799803Z"}
 {"taskCreatedAt":"2025-11-09T22:56:18.897655607Z","taskDependencies":[],"taskId":"t-1s8ADC0","taskNamespace":"Biz/PodcastItLater.hs","taskParent":null,"taskStatus":"Done","taskTitle":"Make PodcastItLater UI mobile-friendly and responsive","taskType":"WorkTask","taskUpdatedAt":"2025-11-09T23:09:16.712244322Z"}
+{"taskCreatedAt":"2025-11-10T01:32:42.893029428Z","taskDependencies":[],"taskId":"t-64tkB5","taskNamespace":"Biz/PodcastItLater.hs","taskParent":null,"taskStatus":"InProgress","taskTitle":"Add dark mode support to PodcastItLater UI","taskType":"WorkTask","taskUpdatedAt":"2025-11-10T01:32:46.388157028Z"}
diff --git a/Biz/PodcastItLater/Web.py b/Biz/PodcastItLater/Web.py
index 2032746..39e2240 100644
--- a/Biz/PodcastItLater/Web.py
+++ b/Biz/PodcastItLater/Web.py
@@ -52,6 +52,60 @@ from typing import override
 
 logger = Log.setup()
 
+
+def create_theme_switcher_script() -> html.script:
+    """Create JavaScript for theme switching with localStorage persistence."""
+    return html.script(
+        """
+        // Theme switcher with localStorage persistence
+        (function() {
+            const getStoredTheme = () => localStorage.getItem('theme');
+            const setStoredTheme = (theme) => {
+                localStorage.setItem('theme', theme);
+            };
+            const getPreferredTheme = () => {
+                const storedTheme = getStoredTheme();
+                if (storedTheme) {
+                    return storedTheme;
+                }
+                return window.matchMedia('(prefers-color-scheme: dark)').matches
+                    ? 'dark' : 'light';
+            };
+
+            const setTheme = theme => {
+                document.documentElement.setAttribute('data-bs-theme', theme);
+                const icon = document.getElementById('theme-icon');
+                if (icon) {
+                    icon.className = theme === 'dark'
+                        ? 'bi bi-sun-fill'
+                        : 'bi bi-moon-fill';
+                }
+            };
+
+            // Set theme on page load
+            setTheme(getPreferredTheme());
+
+            // Theme toggle button handler
+            window.toggleTheme = () => {
+                const currentTheme = document.documentElement
+                    .getAttribute('data-bs-theme');
+                const newTheme = currentTheme === 'dark' ? 'light' : 'dark';
+                setTheme(newTheme);
+                setStoredTheme(newTheme);
+            };
+
+            // Listen for system theme changes
+            window.matchMedia('(prefers-color-scheme: dark)')
+                .addEventListener('change', e => {
+                    if (!getStoredTheme()) {
+                        setTheme(e.matches ? 'dark' : 'light');
+                    }
+                });
+        })();
+        """,
+    )
+
+
 # Configuration
 area = App.from_env()
 BASE_URL = os.getenv("BASE_URL", "http://localhost:8000")
@@ -649,24 +703,49 @@ class BillingPage(Component[AnyChildren, BillingPageAttrs]):
                 ),
                 html.div(
                     html.div(
-                        html.h1(
-                            html.i(classes=["bi", "bi-credit-card", "me-2"]),
-                            "Billing & Usage",
-                            classes=["mb-4"],
-                        ),
                         html.div(
-                            html.a(
-                                html.i(classes=["bi", "bi-arrow-left", "me-1"]),
-                                "Back to Dashboard",
-                                href="/",
-                                classes=[
-                                    "btn",
-                                    "btn-outline-secondary",
-                                    "mb-4",
-                                ],
+                            html.h1(
+                                html.i(
+                                    classes=["bi", "bi-credit-card", "me-2"],
+                                ),
+                                "Billing & Usage",
+                                classes=["mb-4"],
+                            ),
+                            html.div(
+                                html.a(
+                                    html.i(
+                                        classes=["bi", "bi-arrow-left", "me-1"],
+                                    ),
+                                    "Back to Dashboard",
+                                    href="/",
+                                    classes=[
+                                        "btn",
+                                        "btn-outline-secondary",
+                                        "mb-4",
+                                    ],
+                                ),
+                            ),
+                            classes=["flex-grow-1"],
+                        ),
+                        html.button(
+                            html.i(
+                                id="theme-icon",
+                                classes=["bi", "bi-moon-fill"],
                             ),
+                            on_click="toggleTheme()",
+                            classes=[
+                                "btn",
+                                "btn-outline-secondary",
+                                "position-absolute",
+                                "top-0",
+                                "end-0",
+                                "mt-3",
+                                "me-3",
+                            ],
+                            title="Toggle dark mode",
+                            type="button",
                         ),
-                        classes=["mb-4"],
+                        classes=["position-relative", "mb-4"],
                     ),
                     # Success/Error alerts
                     html.div(
@@ -803,6 +882,8 @@ class BillingPage(Component[AnyChildren, BillingPageAttrs]):
                     integrity="sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL",
                     crossorigin="anonymous",
                 ),
+                # Theme switcher script
+                create_theme_switcher_script(),
             ),
         )
 
@@ -936,15 +1017,36 @@ class HomePage(Component[AnyChildren, HomePageAttrs]):
                 html.div(
                     # Header
                     html.div(
-                        html.h1(
-                            "PodcastItLater",
-                            classes=["display-4", "mb-2"],
+                        html.div(
+                            html.h1(
+                                "PodcastItLater",
+                                classes=["display-4", "mb-2"],
+                            ),
+                            html.p(
+                                "Convert web articles to podcast episodes",
+                                classes=["lead", "text-muted"],
+                            ),
+                            classes=["text-center", "flex-grow-1"],
                         ),
-                        html.p(
-                            "Convert web articles to podcast episodes",
-                            classes=["lead", "text-muted"],
+                        html.button(
+                            html.i(
+                                id="theme-icon",
+                                classes=["bi", "bi-moon-fill"],
+                            ),
+                            on_click="toggleTheme()",
+                            classes=[
+                                "btn",
+                                "btn-outline-secondary",
+                                "position-absolute",
+                                "top-0",
+                                "end-0",
+                                "mt-3",
+                                "me-3",
+                            ],
+                            title="Toggle dark mode",
+                            type="button",
                         ),
-                        classes=["text-center", "mb-4", "pt-4"],
+                        classes=["position-relative", "mb-4", "pt-4"],
                     ),
                     # Error alert
                     html.div(
@@ -1078,6 +1180,8 @@ class HomePage(Component[AnyChildren, HomePageAttrs]):
                     integrity="sha384-C6RzsynM9kWDrMNeT87bh95OGNyZPhcTNXj1NW7RuBCsyN/o0jlpcV8Qyq46cDfL",
                     crossorigin="anonymous",
                 ),
+                # Theme switcher script
+                create_theme_switcher_script(),
             ),
         )