## Summary
Replace the single `metadataVersion` integer with per-entity-type
**collection hashes** for granular metadata staleness detection. The
backend already generates a UUID per flat entity map on each cache
recompute (`crypto.randomUUID()` in `WorkspaceCacheService`); we now
expose these via the minimal metadata endpoint and SSE events so the
frontend can compare and know exactly which entity types are stale.
### Key changes
**Backend:**
- `WorkspaceCacheService.getCacheHashes()` — new public method that
reads only `:hash` keys from Redis without fetching full data
- `MinimalMetadataDTO` — added `collectionHashes: Record<string,
string>` (JSON scalar mapping `AllMetadataName` → collection hash),
removed `metadataVersion`
- `MetadataEventDTO` — added optional `updatedCollectionHash` field to
SSE events
- `MetadataEventsToDbListener` — reads the collection hash for the
affected entity type after cache invalidation and attaches it to the SSE
event before publishing
- `MinimalMetadataService` — no longer queries the workspace table; uses
`getCacheHashes()` for all flat entity maps and maps cache keys to
`AllMetadataName` locally
**Frontend:**
- `metadataCollectionHashesState` — new Jotai atom with
`atomWithStorage` + `getOnInit: true` storing
`Partial<Record<MetadataEntityKey, string>>`
- `mapAllMetadataNameToEntityKey()` — explicit mapping from backend
`AllMetadataName` to frontend `MetadataEntityKey` (23 entries)
- `useLoadMinimalMetadata` — stores `collectionHashes` from server,
computes `staleEntityKeys` by comparing local vs server hashes
- `patchMetadataStoreFromSSEEvent()` — accepts optional
`updatedCollectionHash` and updates `metadataCollectionHashesState`
- All 11 SSE effect components — pass
`eventDetail.updatedCollectionHash` through to the patch function
- `useStaleMetadataEntities` — new hook returning entity keys missing
from collection hashes (not yet loaded/synced)
- `resetMetadataStore()` — also clears collection hashes
- Deleted `metadataVersionState` (superseded by collection hashes)
### Design decisions
- **No change to hash generation** — existing `crypto.randomUUID()` is
sufficient. Hashes are persisted in Redis, survive server restarts, and
change only on `invalidateAndRecompute`.
- **"Collection hash" naming** — used consistently to clarify the hash
represents an entire entity collection (e.g., all views), not a single
record.
- **Mapping localized** — backend `WorkspaceCacheKeyName` →
`AllMetadataName` mapping lives in the minimal metadata service.
Frontend `AllMetadataName` → `MetadataEntityKey` mapping lives in a
local utility. Nothing in `twenty-shared`.
- **Backward compatible** — `collectionHashes` is additive;
`updatedCollectionHash` is nullable.
