fix: Strava API breaking changes (effective June 1, 2027)

[cagnulein]

Summary

Strava announced breaking changes to their API effective June 1, 2027:

• Authorization tokens must be sent in request headers, not form params
• The API base URL is changing from https://www.strava.com/api/v3 to https://www.api-v3.strava.com

Changes in homeform::strava_upload_file() (src/homeform.cpp):

• Updated upload URL: https://www.strava.com/api/v3/uploads → https://www.api-v3.strava.com/uploads
• Removed access_token multipart form field
• Added Authorization: Bearer <token> request header

The OAuth token endpoints (/oauth/token, /oauth/authorize) are not affected by this change.

Test plan

• Connect Strava account and upload a workout — verify it appears on Strava
• Verify token refresh still works correctly before upload

🤖 Generated with Claude Code

[cagnulein]

I tested the Strava upload flow on Android with Experimental → Debug Log enabled, after Roberto had already linked Strava successfully.

Findings from the device logs:

• Token refresh succeeds, so authentication itself is OK:
  • strava_refreshtoken() returns HTTP 200 and a valid bearer token response.
• FIT generation succeeds before upload:
  • FitDatabaseProcessor processes the generated .fit file.
  • strava_upload_file_prepare() is called with the FIT path.
• Upload then fails before reaching Strava because the new host does not resolve yet:
  • QNetworkReply::HostNotFoundError
  • Host www.api-v3.strava.com not found
  • HTTP status code 0

This matches Strava's developer-program email: the API base URL changes from https://www.strava.com/api/v3 to https://www.api-v3.strava.com, but only effective June 1, 2027. Today the new hostname is not live yet, so using it now breaks uploads.

Suggested fix for this PR:

1. Keep sending OAuth/access tokens in the Authorization: Bearer ... request header (that part is good and future-compatible).
2. Do not switch the upload base URL to https://www.api-v3.strava.com until the 2027 cutover, or implement a fallback/time-gated endpoint selection.
   • Current working upload endpoint for now: https://www.strava.com/api/v3/uploads
   • Future announced endpoint: https://www.api-v3.strava.com/uploads
3. Also fix the completion handler: writeFileCompleted() currently shows/logs success even after errorOccurredUploadStrava() fires. It should check reply->error() == QNetworkReply::NoError before showing Strava Upload Completed!.

[stale]

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