Add location history search (by address or date range)

[dcondrey]

Difficulty: Moderate

Add the ability to search location history:

CLI:

location-tracker search "coffee shop" --days 30
location-tracker search --near 32.745,-117.155 --radius 100m

Dashboard: Add a search bar above the timeline that filters markers/path by address text match.

Where to look:

• `db.py` — add `search_locations(query, days, near_lat, near_lon, radius)`
• `main.py` — add `search` subcommand
• `static/app.js` — add search input and filter logic

[dcondrey]

Partially implemented. Date range filtering works via the dashboard UI (1/3/7/30/90 days dropdown), /api/locations?days=N endpoint, and history --days CLI flag. Still missing: address/text search across location history.