docs(readme): link Android app doc and adopt app favicon as title icon

Add the Android client design doc to the For Developers section, point
the Supported Devices table at it, and replace the emoji title icon
with the app's book-open favicon (Tokyo Night #7aa2f7) to match the
actual product branding.

README.md

@@ -1,4 +1,4 @@
-# 📚 Bookhoard
+# <img src="web/static/favicon.svg" width="32" alt="Bookhoard logo"> Bookhoard
 
 A modern self-hosted media library system built with Go, PostgreSQL, HTMX, and Tailwind CSS featuring **universal cross-device sync**, beautiful dark themes, and comprehensive media management.
 
@@ -111,6 +111,7 @@ The first user to register automatically becomes an admin.
 ### For Developers
 
 - **[docs/developer/api/api-reference.md](docs/developer/api/api-reference.md)** - Complete API documentation
+- **[docs/developer/android-app.md](docs/developer/android-app.md)** - Android app design & roadmap
 - **[docs/contributing/development.md](docs/contributing/development.md)** - Development workflow
 
 ---
@@ -122,7 +123,7 @@ The first user to register automatically becomes an admin.
 | **Web Browser**  | ✅   | ✅   | Full support                                                  |
 | **KOReader**     | ✅   | ✅   | Runs on Kindle, Kobo, PocketBook hardware                     |
 | **Kobo Devices** | 🚧   | 🚧   | Native Kobo sync coming soon (use KOReader on Kobo today)     |
-| **Mobile Apps**  | 🚧   | 🚧   | Android/iOS apps coming later                                 |
+| **Mobile Apps**  | 🚧   | 🚧   | Native Android app in design ([docs](docs/developer/android-app.md)); iOS later |
 
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