feat(map): replace Google Maps + OSMDroid with unified MapLibre Compose Multiplatform

Replace the dual flavor-specific map implementations (Google Maps for google,
OSMDroid for fdroid) with a single MapLibre Compose Multiplatform implementation
in feature:map/commonMain, eliminating ~8,500 lines of duplicated code.

Key changes:
- Add maplibre-compose v0.12.1 dependency (KMP: Android, Desktop, iOS)
- Create unified MapViewModel with camera persistence via MapCameraPrefs
- Create MapScreen, MaplibreMapContent, NodeTrackLayers, TracerouteLayers,
  InlineMap, NodeTrackMap, TracerouteMap, NodeMapScreen in commonMain
- Create MapStyle enum with predefined OpenFreeMap tile styles
- Create GeoJsonConverters for Node/Waypoint/Position to GeoJSON
- Move TracerouteMapScreen from feature:node/androidMain to commonMain
- Wire navigation to use direct imports instead of CompositionLocal providers
- Delete 61 flavor-specific map files (google + fdroid source sets)
- Remove 8 CompositionLocal map providers from core:ui
- Remove SharedMapViewModel (replaced by new MapViewModel)
- Remove dead google-maps and osmdroid entries from version catalog
- Add MapViewModelTest with 10 test cases in commonTest

Baseline verified: spotlessCheck, detekt, assembleGoogleDebug, allTests all pass.

core/repository/src/commonMain/kotlin/org/meshtastic/core/repository/AppPreferences.kt

@@ -171,6 +171,41 @@ interface MapPrefs {
     fun setLastHeardTrackFilter(seconds: Long)
 }
 
+/** Reactive interface for map camera position persistence. */
+interface MapCameraPrefs {
+    val cameraLat: StateFlow<Double>
+
+    fun setCameraLat(value: Double)
+
+    val cameraLng: StateFlow<Double>
+
+    fun setCameraLng(value: Double)
+
+    val cameraZoom: StateFlow<Float>
+
+    fun setCameraZoom(value: Float)
+
+    val cameraTilt: StateFlow<Float>
+
+    fun setCameraTilt(value: Float)
+
+    val cameraBearing: StateFlow<Float>
+
+    fun setCameraBearing(value: Float)
+
+    val selectedStyleUri: StateFlow<String>
+
+    fun setSelectedStyleUri(value: String)
+
+    val hiddenLayerUrls: StateFlow<Set<String>>
+
+    fun setHiddenLayerUrls(value: Set<String>)
+
+    val networkMapLayers: StateFlow<Set<String>>
+
+    fun setNetworkMapLayers(value: Set<String>)
+}
+
 /** Reactive interface for map consent. */
 interface MapConsentPrefs {
     fun shouldReportLocation(nodeNum: Int?): StateFlow<Boolean>
@@ -238,6 +273,7 @@ interface AppPreferences {
     val emoji: CustomEmojiPrefs
     val ui: UiPrefs
     val map: MapPrefs
+    val mapCamera: MapCameraPrefs
     val mapConsent: MapConsentPrefs
     val mapTileProvider: MapTileProviderPrefs
     val radio: RadioPrefs