Add missing godoc comments to:
- NewRateLimiter and Allow in ratelimit.go
- SnapshotSyncStatus in temperature_proxy.go
- NewClient and GetVersion in pkg/pmg/client.go
Related to #614
Corrects three issues with PMG monitoring:
1. Remove unsupported timeframe parameter from GetMailStatistics
- PMG API /statistics/mail does not accept timeframe parameter
- Previously sent "timeframe=day" causing 400 error
- API returns current day statistics by default
2. Fix GetMailCount timespan parameter to use seconds
- Changed from 24 (hours) to 86400 (seconds)
- PMG API expects timespan in seconds, not hours
- Previously sent "timespan=24" causing 400 error
3. Update function signature and tests
- Renamed GetMailCount parameter from timespanHours to timespanSeconds
- Updated test expectations to match corrected API calls
- Tests verify parameters are sent correctly
These changes align the PMG client with actual PMG API requirements,
fixing the data population issues reported in v4.25.0.
