feat: add client-side Level/Event filters to Log Entries

The backend rejects `level`/`event` as x:Log/query filter conditions
(unsupportedFilter), even though both are already returned per row.
Since a real fix requires backend changes outside this repo, the two
filters are injected into the schema client-side (clientOnly flag) and
applied entirely in the browser: excluded from the JMAP filter sent to
the server, and used to narrow an eagerly-fetched, locally-paginated
result set instead.

Also makes large enum filters (Event has 634 values) render as a
searchable Combobox instead of a plain Select, generically for any
list with more than 15 enum options.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/i18n/en.json

@@ -289,6 +289,8 @@
     "bulkSuccessUpdate_one": "{{count}} item updated successfully.",
     "bulkSuccessUpdate_other": "{{count}} items updated successfully.",
     "clearSelection": "Clear selection",
+    "comboboxEmptyText": "No matches.",
+    "comboboxSearchPlaceholder": "Search...",
     "confirmDescription": "Are you sure you want to proceed with: {{action}}?",
     "confirmTitle": "Confirm Action",
     "create": "Create {{name}}",