feat(server): initial implementation

This commit captures the full server code accumulated across
several development sessions. It includes the following layers,
applied in roughly this order during development:

1. Base infrastructure
   - cmd/poc-server HTTP+WebSocket server, /health, /stats
   - internal/transport wire types (Envelope + all message types)
   - internal/catalog, internal/realtime, internal/stats
   - internal/storage/postgres with migrations 001-004
   - .env, .env.example, docker-compose, Dockerfile, scripts/

2. Swagger documentation
   - go get github.com/swaggo/http-swagger
   - swag init produces docs/docs.go
   - /swagger/index.html UI, /swagger/doc.json spec
   - annotations on health/stats/ws and catalog handlers

3. Races API
   - internal/races/{store,service,keyset,types}.go
   - migration 005_races.sql: finished_races, race_plans, race_queue
   - GET /api/races with keyset pagination, status filter
   - GET /api/races/upcoming
   - POST /api/races/queue/join, GET, DELETE
   - POST/GET /api/races/plans, DELETE /{id}
   - lobby.RaceMeta simplification (no host_id/host_name)

4. Races seeder
   - internal/races/seed with deterministic generator
   - --seed-races / --reset CLI flags in main.go
   - 30 finished + 5 live + 5 plans + 4 queue entries

5. Drivers and clans
   - internal/drivers, internal/clans (CRUD, validation)
   - migration 008_drivers_clans.sql
   - /api/clans and /api/drivers endpoints
   - 3-letter uppercase nickname/tag validation
   - lobby.DriverMeta: Nickname, AvatarURL, ClanID, ClanTag

6. Podium
   - internal/transport.RacePodiumEntry
   - lobby.SetDriverProfile for in-memory metadata sync
   - migration 007_podium.sql (podium JSONB column)
   - seeder populates top-3 per finished race

7. Live races persistence
   - migration 009_live_persistence.sql: live_races,
     live_race_drivers, lobby_drivers
   - internal/races/live_store.go: LiveStore with write-side
     mirror for lobby.Service mutations
   - Service.collectLive and Upcoming read from Postgres
   - main.go RestoreFromDB rehydrates lobby on startup

8. Unify live + finished into one races table
   - migration 010_unify_races.sql: rename finished_races to
     races, expand status CHECK, merge live rows
   - PgStore now hosts both write paths; LiveStore is a
     thin facade implementing lobby.Persistence
   - seeder resetAll drops only finished/cancelled rows and
     race_plans / race_queue / lobby_drivers

Each layer is consistent on its own; cross-layer changes are
visible in the file history. A future refactor may split this
commit into the per-stage boundaries listed above.

server/internal/storage/postgres/migrations/007_podium.sql

@@ -0,0 +1,16 @@
+-- 007_podium.sql — add podium to finished_races.
+--
+-- Podium is the top-3 finishers of a completed race. Stored as JSONB
+-- (a small ordered list, rarely queried as a relation). Shape per row:
+--   { "position": 1, "driver_id": "driver-alice",
+--     "name": "driver-alice", "total_time_ms": 123456 }
+--
+-- Ordering: position 1 first.
+-- GIN index over the jsonb lets future UI filters (e.g. "races won by
+-- driver X") use @> containment queries without a schema change.
+
+ALTER TABLE finished_races
+    ADD COLUMN IF NOT EXISTS podium JSONB NOT NULL DEFAULT '[]'::jsonb;
+
+CREATE INDEX IF NOT EXISTS finished_races_podium_gin
+    ON finished_races USING GIN (podium);