Add 'Find it' hot/cold RSSI finder + 'Make it ring' (GATT)

- FinderScreen: live smoothed RSSI as a growing, colour-shifting proximity meter (works on silent/modified tags that refuse to ring). Fed by ScanService.finderRssi (every advert, ahead of the DB throttle).
- TrackerRinger: user-initiated GATT play-sound — VIGIL's one active operation (detection stays passive). DULT cross-vendor path (Google FMDN + DULT partners) implemented; Apple/others report gracefully pending per-ecosystem UUIDs (GATT protocol research in progress). UUIDs/opcode pending on-device verification.
- Detail sheet: 'Find it' + 'Ring it' buttons; TrackerEntity.lastMac added (needed to GATT-connect); DB version 3.
- BLUETOOTH_CONNECT was already declared for this.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0187UiEtasyowhEBYs6s9iF5

app/src/main/kotlin/org/soulstone/vigil/data/TrackerRepository.kt

@@ -122,7 +122,8 @@ class TrackerRepository(private val db: VigilDatabase) {
             lastRssi = obs.rssi,
             peakRssi = maxOf(existing?.peakRssi ?: -127, obs.rssi),
             distinctPlaces = assessment.distinctPlaces,
-            effectiveSightings = assessment.sightings
+            effectiveSightings = assessment.sightings,
+            lastMac = obs.mac
         )
         db.trackerDao().upsert(updated)
         RecordResult(updated, newlyAlerting)

app/src/main/kotlin/org/soulstone/vigil/data/db/VigilDatabase.kt

@@ -37,7 +37,9 @@ data class TrackerEntity(
     val lastRssi: Int = 0,
     val peakRssi: Int = -127,
     val distinctPlaces: Int = 0,
-    val effectiveSightings: Int = 0
+    val effectiveSightings: Int = 0,
+    // last-seen BLE MAC — needed to GATT-connect for "make it ring"
+    val lastMac: String = ""
 )
 
 /** One sighting of a tracker at one instant, geotagged when a fix is available. */
@@ -114,7 +116,7 @@ interface PlaceDao {
 
 @Database(
     entities = [TrackerEntity::class, SightingEntity::class, PlaceEntity::class],
-    version = 2,
+    version = 3,
     exportSchema = false
 )
 abstract class VigilDatabase : RoomDatabase() {