Implement automatic Garmin token refresh and fix expiry tracking

- Add OAuth1 to OAuth2 token exchange using Garmin's exchange endpoint
- Track refresh token expiry (~30 days) instead of access token expiry (~21 hours)
- Auto-refresh access tokens in cron sync before they expire
- Update Python script to output refresh_token_expires_at
- Add garminRefreshTokenExpiresAt field to User type and database schema
- Fix token input UX: show when warning active, not just when disconnected
- Add Cache-Control headers to /api/user and /api/garmin/status to prevent stale data
- Add oauth-1.0a package for OAuth1 signature generation

The system now automatically refreshes OAuth2 tokens using the stored OAuth1 token,
so users only need to re-run the Python auth script every ~30 days (when refresh
token expires) instead of every ~21 hours (when access token expires).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -29,6 +29,9 @@ importers:
       node-cron:
         specifier: ^4.2.1
         version: 4.2.1
+      oauth-1.0a:
+        specifier: ^2.2.6
+        version: 2.2.6
       pino:
         specifier: ^10.1.1
         version: 10.1.1
@@ -1773,6 +1776,9 @@ packages:
   node-releases@2.0.27:
     resolution: {integrity: sha512-nmh3lCkYZ3grZvqcCH+fjmQ7X+H0OeZgP40OierEaAptX4XofMh5kwNbWh7lBduUzCcV/8kZ+NDLCwm2iorIlA==}
 
+  oauth-1.0a@2.2.6:
+    resolution: {integrity: sha512-6bkxv3N4Gu5lty4viIcIAnq5GbxECviMBeKR3WX/q87SPQ8E8aursPZUtsXDnxCs787af09WPRBLqYrf/lwoYQ==}
+
   obug@2.1.1:
     resolution: {integrity: sha512-uTqF9MuPraAQ+IsnPf366RG4cP9RtUi7MLO1N3KEc+wb0a6yKpeL0lmk2IB1jY5KHPAlTc6T/JRdC/YqxHNwkQ==}
 
@@ -3445,6 +3451,8 @@ snapshots:
 
   node-releases@2.0.27: {}
 
+  oauth-1.0a@2.2.6: {}
+
   obug@2.1.1: {}
 
   on-exit-leak-free@2.1.2: {}