feat(actions): add branch filters to run list (#37826)

## Summary

- Add a Branch filter dropdown to the repo Actions run list web UI
- Wire `?branch=` query param through the web handler, matching the
existing REST API filter behavior
- Source the Branch dropdown from the indexed `branch` table (filtering
out deleted branches) instead of scanning `action_run.ref`, addressing
review feedback about unindexed columns

The Event filter was dropped after review: a static list of supported
events was noisy as UX, and querying distinct values from
`action_run.trigger_event` is slow because the column is not indexed.
`FindRunOptions.TriggerEvent` is kept for the REST API.

Closes #25042

---------

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

options/locale/locale_en-US.json

@@ -3776,6 +3776,8 @@
   "actions.runs.status": "Status",
   "actions.runs.actors_no_select": "All actors",
   "actions.runs.status_no_select": "All status",
+  "actions.runs.branch": "Branch",
+  "actions.runs.branches_no_select": "All branches",
   "actions.runs.no_results": "No results matched.",
   "actions.runs.no_workflows": "There are no workflows yet.",
   "actions.runs.no_workflows.quick_start": "Don't know how to start with Gitea Actions? See <a target=\"_blank\" rel=\"noopener noreferrer\" href=\"%s\">the quick start guide</a>.",