feat: integrate Tauri v2 with Android widget and voice assistant

- Add Tauri v2 shell (Cargo, tauri.conf.json, capabilities, plugins)
- Migrate all fetch() calls to apiFetch() for Tauri-aware HTTP
- Migrate WebSocket endpoints to resolveEndpoints() for dynamic URLs
- Add ServerConfigDialog for remote server URL configuration
- Add tauri.ts lib with isTauri detection, apiFetch wrapper, plugin helpers
- Add server-config Pinia store with persistence via plugin-store
- Conditional PWA (disabled in Tauri builds)
- Android: home screen transcript widget (last 5 messages, 30s refresh)
- Android: voice command / share activity (SpeechRecognizer + WebSocket)
- Android: signed release APK with auto-copy to installers/
- Remove stale frontend/src-tauri directory

.gitignore

@@ -9,6 +9,39 @@ nul
 # Voice recordings (training data)
 server/recordings/*.webm
 
+# Tauri build artifacts
+src-tauri/target/
+src-tauri/installers/
+
+# Tauri gen: ignore everything except our custom Android sources
+src-tauri/gen/*
+!src-tauri/gen/android/
+src-tauri/gen/android/*
+!src-tauri/gen/android/app/
+src-tauri/gen/android/app/*
+!src-tauri/gen/android/app/build.gradle.kts
+!src-tauri/gen/android/app/src/
+src-tauri/gen/android/app/src/*
+!src-tauri/gen/android/app/src/main/
+src-tauri/gen/android/app/src/main/*
+!src-tauri/gen/android/app/src/main/AndroidManifest.xml
+!src-tauri/gen/android/app/src/main/java/
+!src-tauri/gen/android/app/src/main/res/
+src-tauri/gen/android/app/src/main/res/*
+!src-tauri/gen/android/app/src/main/res/layout/
+src-tauri/gen/android/app/src/main/res/layout/*
+!src-tauri/gen/android/app/src/main/res/layout/widget_transcript.xml
+!src-tauri/gen/android/app/src/main/res/xml/
+src-tauri/gen/android/app/src/main/res/xml/*
+!src-tauri/gen/android/app/src/main/res/xml/transcript_widget_info.xml
+!src-tauri/gen/android/app/src/main/res/values/
+src-tauri/gen/android/app/src/main/res/values/*
+!src-tauri/gen/android/app/src/main/res/values/strings.xml
+src-tauri/gen/android/keystore.jks
+
+# Old frontend Tauri location
+frontend/src-tauri/
+
 # Agent runtime data
 .claude-*/plugins/
 .claude-*/plans/