UTC-align historical chunks (SolarEdge + Enphase)

BOLT-958. Branch artem-agent/utc-align-historical-chunks. Worktree at ../mono-utc-align-historical-chunks. Apply 3 changes to createTimeChunks() in SolarEdge + Enphase monitoring API coordinators: (1) floor currentStart to startOf(day), (2) advance cursor by MAX_CHUNK_SIZE_DAYS instead of currentEnd, (3) add input validation matching EG4 pattern (historicalCoordinator.ts:54-62). Update existing chunker tests for new UTC-day alignment + validation throws. Open PR as DRAFT — Artem will merge himself; agent must not merge.