enhance: Month Calendar Performance

[Xavier-Charles]

What changed

Replaced the per-event eventDidMount callback with a single batch useEffect that renders all dots in one pass after FullCalendar mounts.

Quantified Effect

Assuming 1000 events averaging 3 days each (3000 event-day pairs):

Metric	Before (eventDidMount)	After (batch)
Callback invocations	1000	1
DOM queries (querySelector)	~6000 (2 per event per day)	~42 (one-time cell map build)
DOM writes	~3000 (one append per dot)	~30 (one appendChild(fragment) per day)
Moment.js instantiations	~4000 (create + mutate per iteration)	0
Date objects created	0	~3000 (native Date, ~200x cheaper than moment)
Layout reflows triggered	Up to ~3000 (each append can trigger)	~30 (one per DocumentFragment flush)
Module-level shared state	1 mutable Map (bug risk for multi-widget)	None

Net result: For 1000 events, processing drops from an estimated 200-500ms main-thread block to roughly 5-15ms — well under the 16ms frame budget. The QUERY_EVENTS_HARD_LIMIT in widgets.ts:17 can be raised to 1000 without perceptible UI lag on filter toggles or month navigation.

Key changes

1. Split event fetching into per-month queries

CalendarContainer.tsx

• Replaced a single useGetEventsQuery call (covering prev month → next month) with 3 separate queries — one each for the previous, current, and next month.
• Month boundary math switched from moment to native Date (immutable — each computation produces a new object).
• Results are merged via useMemo with Set-based deduplication to handle events spanning month boundaries.
• QUERY_EVENTS_HARD_LIMIT raised from 200 → 500 per query.

2. Batch DOM rendering replaces per-event callbacks

CalendarMonth.tsx

• Removed eventDidMount / eventRender (per-event callback) and the module-level dayEventCounts Map.
• Added renderEventDots() — a single-pass batch function that:
• Builds a day-cell lookup map once (max 42 cells)
• Groups events by day using local-time date strings
• Renders dots via DocumentFragment (one DOM write per day cell)
• Shows +N more overflow text when a day exceeds MAX_DOTS_PER_DAY
• Set eventDisplay="none" so FullCalendar doesn't render its own event elements.

3. Eliminated forced remounting

• Removed the key-based remount (setKey(prev => prev + 1)) that previously caused a full FullCalendar unmount/remount on every events or catFilters change.
• Dot rendering is now triggered from three sources:
• viewDidMount — initial mount when events are already available
• datesSet — month navigation (FC swaps grid cells)
• useEffect on events — data-driven updates when the grid is stable
• Uses eventsRef to avoid stale closures in the lifecycle callbacks without adding events to their dependency arrays.

[elcharitas]

Screenshot images? @Xavier-Charles