Handle Strava rate limiting with abort, retry time and daily usage display

Strava sync for 167 rides exceeds the 100/15-min read limit (2 calls per ride).
Previously a 429 was treated as a skipped ride, so every remaining ride also
failed silently. Now GetJSON returns a typed RateLimitError with RetryAfter
computed from Retry-After/Date and X-RateLimit headers (15-min window resets
at :00/:15/:30/:45, daily at midnight UTC) and tracks Read/Overall usage.
syncRides aborts on 429 with partial progress instead of skipping, and
handleSync emits an SSE error with retry time, daily usage vs limit and
structured rateLimit snapshot; progress and complete events also carry the
snapshot for the UI to display. Frontend shows Read daily/15-min usage in
progress details and on completion.

0 files changed, 0 insertions, 0 deletions