Add race and station management

- races table: name, date, description, is_active
- stations table: ordered checkpoints with GPS per race
- New /api/races and /api/races/{id}/stations endpoints
- Upload now requires race + station selection; uses station GPS
  so images without GPS EXIF are accepted
- passages filtered by active race throughout
- RacePage: create races, manage stations (add/edit/delete checkpoints)
- Navbar shows active race name
- Start and finish stations created automatically per race

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/profile_db.py

@@ -25,6 +25,7 @@ async def init_db(db: aiosqlite.Connection) -> None:
 
         CREATE TABLE IF NOT EXISTS passages (
             passage_id      TEXT PRIMARY KEY,
+            race_id         TEXT REFERENCES races(race_id),
             profile_id      TEXT REFERENCES athletes(profile_id),
             bib_number      TEXT,
             station         TEXT NOT NULL,
@@ -50,12 +51,16 @@ async def init_db(db: aiosqlite.Connection) -> None:
         );
 
         CREATE INDEX IF NOT EXISTS idx_passages_profile ON passages(profile_id);
+        CREATE INDEX IF NOT EXISTS idx_passages_race ON passages(race_id);
         CREATE INDEX IF NOT EXISTS idx_passages_station ON passages(station);
         CREATE INDEX IF NOT EXISTS idx_passages_needs_review ON passages(needs_review);
         CREATE INDEX IF NOT EXISTS idx_passage_images_passage ON passage_images(passage_id);
     """)
     await db.commit()
 
+    from race_db import init_race_tables
+    await init_race_tables(db)
+
 
 async def get_db() -> aiosqlite.Connection:
     db = await aiosqlite.connect(DB_PATH)