feat(teams): add Fienta as primary Discord->team source (sheet fallback)

The registration-log sheet only has in-game nicknames, so matching Discord
users to teams failed for ~10 of 40 teams. Fienta collects each competitor's
Discord username (+ sometimes user ID) and team name per ticket, giving a
reliable Discord-identity -> team mapping (validated: 201 usernames, 42 teams).

- core/fienta.py: token-auth client; fetch /events/{id}/tickets?attendees=true,
  parse competitor/coach/substitute tickets into {username|id -> team} and
  {team -> game}; exclude visitor/supporter/LAN/early-bird/waiting-list. No-op
  when FIENTA_API_TOKEN/FIENTA_EVENT_ID unset.
- member_sync: resolve_team() tries Fienta (id, then username) then the sheet;
  all_managed_team_names() and team_dividers() merge both sources.
- /teamsync + hourly task refresh Fienta alongside the sheet; enabled when
  either source is configured.
- config + .env.example: FIENTA_API_TOKEN, FIENTA_EVENT_ID.
- tests: fienta parsing (game detection, inclusion rules, id/username mapping).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XPRsW4tazVtYi2jNzVQkre

.gitignore

@@ -9,4 +9,7 @@ pocketbase.exe
 pocketbase
 pb_data/
 pb_migrations/
-logs/
+logs/
+fientalog
+fientatickets
+fientaorders