fix(trailbase-db-collection): handle 403 on subscribe/* with polling fallback

[royalcala]

Problem

When a TrailBase table has row-level access rules (_ROW_.*), the server cannot evaluate those predicates for wildcard subscriptions and returns 403 Forbidden on GET /api/records/v1/<table>/subscribe/*.

This caused two separate bugs:

Bug 1 — Collection stuck in loading state forever

start() called subscribe("*") without any error handling. The thrown 403 error propagated past the finally block, so markReady() was never called → useLiveQuery.data remained undefined indefinitely, even though list requests returned data normally.

Bug 2 — Every optimistic mutation rolled back after 120 s

onInsert, onUpdate, and onDelete called awaitIds() unconditionally. awaitIds waits for the subscription SSE stream to confirm the server has persisted the record by checking seenIds. In polling-only mode seenIds is never populated (no SSE events arrive), so the wait always timed out → TimeoutWaitingForIdsError → the optimistic mutation was rolled back.

Fix

1. Wrap subscribe("*") in try/catch — log a console.debug message and continue without SSE when the subscribe call fails (e.g. 403).
2. Hoist sseAvailable flag to closure scope — set to true only when SSE connects successfully. This allows the three mutation handlers to check it.
3. markReady() is always called via finally — the collection becomes usable even without live updates.
4. onInsert/onUpdate/onDelete skip awaitIds() when !sseAvailable — the collection reflects server state after the next polling cycle instead of timing out.
5. periodicCleanupTask is only started when SSE is actually available — avoids a no-op interval running forever in polling-only mode.

Behaviour after fix

• Tables with open subscribe/* access → unchanged behaviour (SSE + awaitIds as before).
• Tables with row-level access rules that deny subscribe/* → polling-only mode: data loads via list requests, optimistic mutations persist immediately and are confirmed after the next poll.

Repro

// TrailBase config.textproto — row-level rule denies wildcard subscribe
read_access_rule: "_ROW_.user_id = _USER_.id"

• Open the app → collections stuck loading (useLiveQuery.data === undefined)
• Insert a record → appears briefly, then disappears after ~2 min (TimeoutWaitingForIdsError)