fix(alerts): maintenance window revision guard, locked org cap, shared weekdays - #2343

🟢 Confidence 9/10 · safe to merge. The revision guard and recount are pinned by new tests; the advisory lock itself is untested because PGlite serialises transactions.
_{no findings · tests partial −1 · risk medium}

Replaces the millisecond updatedAt guard with a revision column bumped by every write, moves the 100-window cap count inside an org-scoped advisory lock, and de-duplicates the weekday literals. Safe to merge.

• alert_maintenance_windows.revision bumps on every update; syncWindow writes only at the revision it read
• create counts the per-org cap inside pg_advisory_xact_lock(org, 'alert_maintenance_windows')
• MAINTENANCE_WEEKDAYS moves to @maple/domain/http; the MCP copy is deleted

Before merge

• Migration · Check it is safe on production data and with the code still deployed · packages/db/drizzle/20261107115926_alert_maintenance_window_revision/migration.sql

_{d8eee5d · Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}