Create mental health resource geolocation API

Build an API route that returns nearby mental health resources so users in crisis always know where to turn.

GET /api/resources?lat=X&lng=Y&type=crisis|therapy|support&radius=25

Data sources (in priority order):

1. SAMHSA Treatment Locator API (free, no key required) — for therapy and support types
2. A seeded crisis_hotlines database table (always available offline) — for crisis type
3. Hardcoded national fallbacks — always included regardless of type

Response:

{
  resources: Resource[],  // sorted by distance ascending
  source: 'live' | 'cached' | 'fallback',
  fetchedAt: string
}

Caching:

• Cache SAMHSA results in Redis for 24 hours keyed by resources:{lat_2dp}:{lng_2dp}:{type}
• On Redis miss or Redis unavailable, fetch live and cache
• On SAMHSA API error, return cached result or hardcoded fallbacks

Rate limit: 20 req/min per IP using the existing lib/rate-limit.ts utility.

Write unit tests covering: cache hit, SAMHSA live fetch, SAMHSA failure with fallback, missing lat/lng (400 error).