STRAVA-002 — Add a self-service MPRC club-status check without roster scraping

[daliu]

Outcome

Let a connected member check whether their own Strava account currently reports MPRC club membership without building or storing a club roster.

Scope

• Server calls GET /athlete/clubs with that signed-in user's token.
• Match one configured immutable MPRC club ID.
• Return status only to that user and store only a minimal last-check result if policy approves.
• Clearly label the result on-demand and not continuously synchronized.
• Handle missing scope, revoked token, not-member, rate limit, and provider outage with cache/backoff.

Acceptance criteria

• The implementation never uses Club Members/Admins/Activities endpoints scheduled for removal on 2026-09-01.
• No join, approve, or remove action is implied; Strava exposes no such write API.
• The result never grants MPRC website membership, member pricing, or Google/WhatsApp access.
• No other athlete or roster data is stored, exported, or displayed to admins.
• Strava API policy, deletion, and user-only display constraints are tested/documented.

Dependencies

#88 (STRAVA-001).

Official references

• https://developers.strava.com/docs/reference/#api-Clubs-getLoggedInAthleteClubs
• https://developers.strava.com/docs/changelog/
• https://www.strava.com/legal/api_policy

Coordination

Parent: #79

Do not begin implementation until dependencies are complete, this issue is assigned, and a timestamped CLAIMED comment naming the agent and branch is posted. Creation of this ticket is not a claim. Preserve the parallel agent work tracked by stable IDs in GITHUB_ISSUES.md.