api: Territory geometry + spatial lookup endpoints

[victorquinn]

Summary

Implement territory-specific API endpoints for geometry retrieval and spatial point-in-polygon lookups.

Files to Create

• app/api/v1/territories/[id]/geometry/route.ts — GeoJSON geometry with simplification
• app/api/v1/territories/lookup/route.ts — Point-in-polygon lookup

Geometry Endpoint

• Returns GeoJSON for a territory
• ?simplify=0.001 for detail view (~100m precision)
• ?simplify=0.01 for overview (~1km precision)
• Aggressive caching (boundaries rarely change)

Lookup Endpoint

• ?lat=35.78&lng=-78.64 returns all territories containing the point
• Uses bbox pre-filter + ST_Covers for accuracy
• Returns region metadata with territory info

Acceptance Criteria

• Geometry endpoint returns valid GeoJSON
• Simplification reduces vertex count appropriately
• Lookup correctly identifies territories for a point
• Proper caching headers
• npm run build passes

Spec ref: Sections 4.5–4.6
Blocked by: #5, #7
Blocks: Explorer territory migration