feat(go-services): tracker-go — complete the Phase 1 read API

Adds the rest of the read-side endpoints to the Go tracker, all parity-checked
against the live Python service:

- DB reads: /stats/{c}, /portals, /spawns/heatmap, /server-health,
  /character-stats/{c} (stats_data JSONB merged to top level),
  /combat-stats[/{c}], /inventories, /inventory/{c}/search.
- 5-minute totals cache + /total-rares, /total-kills.
- Ingest-only state returned as Python's empty/default shapes (/quest-status,
  /vital-sharing/peers, /equipment-cantrip-state/{c}); /issues (flat file),
  /me (401 until cookie verification lands).
- Streaming reverse proxy to inventory-service (/inventory/{c},
  /inventory-characters, /search/*, /sets/list, /inv/{path...} incl. the SSE
  suitbuilder stream).
- compare/compare_endpoints.py: structural parity for all read endpoints +
  exact-match check for /character-stats and /combat-stats on OFFLINE chars
  (online chars legitimately differ — Python serves a richer live overlay that
  Phase-1 Go lacks until ingest).

Verified live: 14/14 endpoints structural-match, 8/8 rich offline chars
exact-match on /character-stats.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go-services/docker-compose.go.yml

@@ -29,6 +29,7 @@ services:
       PORT: "8770"
       # Read-only use of the same dereth TimescaleDB the Python tracker writes.
       DATABASE_URL: "postgresql://postgres:${POSTGRES_PASSWORD}@db:5432/dereth"
+      INVENTORY_SERVICE_URL: "http://inventory-service:8000"
       LOG_LEVEL: "INFO"
     depends_on:
       - db