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/build.gradle.kts

@@ -0,0 +1,8 @@
+plugins {
+    alias(libs.plugins.android.application) apply false
+    alias(libs.plugins.kotlin.android) apply false
+    alias(libs.plugins.kotlin.compose) apply false
+    alias(libs.plugins.kotlin.serialization) apply false
+    alias(libs.plugins.hilt.android) apply false
+    alias(libs.plugins.ksp) apply false
+}