feat: replace Nominatim geocoding with Google Maps API; add TOC map improvements

Switch geocoding from Nominatim to Google Maps Geocoding API for accurate
local place name resolution (bounds-biased, with 25km distance rejection guard).
Remove the now-unused _get_node_place reverse-geocoder and _node_place_cache.

Map page (TOC improvements):
- Weather radar tiles auto-refresh every 5 minutes via radarEpoch key cycling
- Google Maps traffic overlay added to LayersControl
- Live 24h clock overlay at bottom-left for situational awareness
- Incident sidebar cards now show age (time since dispatch) and unit count

drb-c2-core/app/config.py

@@ -21,6 +21,9 @@ class Settings(BaseSettings):
     openai_api_key: Optional[str] = None
     stt_model: str = "gpt-4o-transcribe"  # whisper-1 | gpt-4o-mini-transcribe | gpt-4o-transcribe
 
+    # Google Maps (geocoding)
+    google_maps_api_key: Optional[str] = None
+
     # Gemini (intelligence extraction, embeddings, incident summaries)
     gemini_api_key: Optional[str] = None
     summary_interval_minutes: int = 2          # how often the summary loop runs