ENG-4412 Add new audit log filtering capabilities to allow filtering for user / identity actor

Greptile Summary

This PR wires up the existing backend actor filter to the frontend audit log search UI, adding an actor_id chip filter with autocomplete suggestions for users and machine identities, plus a mismatch-detection warning when the chosen ID doesn't match the selected actor type. The backend changes extend the ACTOR_TYPE_TO_METADATA_ID_KEY mapping so the correct JSON metadata field is queried for each actor type in both Postgres and ClickHouse DALs.

Key changes:

• New useAuditLogActorSuggestions hook fetches org users (all) and identities (up to 100) to populate autocomplete suggestions for the actor_id filter chip.
• AuditSearchFilter gains an actor_id property with dynamic suggestions and a chip-level warning when the selected ID doesn't appear in the current actor type's suggestion list.
• ACTOR_TYPE_TO_METADATA_ID_KEY constant maps each ActorType to the JSON key used in actorMetadata, replacing the previous hardcoded userId assumption in both DALs.
• Deprecated project router gains an actorType query parameter to match the org router.

Issues found:

• Silent filter bypass (both DALs): When actorId is supplied with an actorType not present in ACTOR_TYPE_TO_METADATA_ID_KEY (e.g. PLATFORM, UNKNOWN_USER), the ID constraint is silently dropped and all logs for that actor type are returned, with no error surfaced to the caller.
• Identity suggestion limit: The hard-coded limit: 100 in useAuditLogActorSuggestions means orgs with more than 100 identities will see truncated suggestions, and the mismatch-detection logic will produce false warnings for valid identities beyond that limit.
• Eager user fetch: fetchOrgUsers is triggered on every Audit Logs page mount regardless of whether the user interacts with the actor_id filter, which is an unnecessary network request for most page views.

Confidence Score: 3/5

• Safe to merge with minor behavioural concerns; no security issues, but the silent actorId filter bypass and the 100-identity cap should be addressed before wide adoption.
• The frontend feature is well-implemented with a nice UX touch (mismatch warnings), and the parameterized backend queries are injection-safe. The score is reduced because of the silent no-op when an unsupported actorType is paired with an actorId (could mislead API consumers), the hard-coded identity limit that causes false mismatch warnings, and the eager user-list fetch on every page load.
• backend/src/ee/services/audit-log/audit-log-dal.ts and audit-log-clickhouse-dal.ts (silent filter bypass); frontend/src/hooks/api/auditLogs/useAuditLogActorSuggestions.ts (identity limit + eager fetch).

Important Files Changed

_{Last reviewed commit: "feat: add actor_id f..."}

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