Add Android app skeleton (Kotlin/Compose, Catppuccin Mocha theme)

Full app scaffold wired to the backend: onboarding, content-length
picker, map screen (permission flow + text-search fallback), guide
screen with a swipeable place-card stack driven by on-device TTS
narration and a 60s re-scan loop, place detail screen with
mute/favorite controls, favorites (Room-backed), and settings.
Hilt for DI, Retrofit+kotlinx.serialization for the API client,
DataStore for onboarding/content-length prefs, FusedLocationProviderClient
for location. The 2GIS MapKit integration is isolated behind
map/DgisMapView.kt (currently a placeholder) since its exact Maven
coordinates need confirming from the 2GIS developer portal.

Verified by actually building it: installed a minimal Android SDK
(platform 34 + build-tools, no emulator) and JDK 17 locally, then ran
:app:compileDebugKotlin, :app:assembleDebug (produced a real debug
APK), and :app:lintDebug (0 errors, 44 non-blocking warnings, mostly
"newer dependency version available"). Caught and fixed two real bugs
this way: a wrong Maven artifact for the Retrofit kotlinx.serialization
converter, and missing ExperimentalMaterial3Api opt-in.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

android/app/src/main/res/values/themes.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+    <!-- Compose drives all real theming (see theme/Theme.kt); this is only the
+         pre-Compose window background shown while the activity inflates. -->
+    <style name="Theme.GuideCity" parent="android:Theme.Material.NoActionBar">
+        <item name="android:windowBackground">@color/catppuccin_base</item>
+        <item name="android:statusBarColor">@color/catppuccin_base</item>
+    </style>
+</resources>