chore: update .gitignore and add review document

- Add SQLite temp files (sub2api*) to .gitignore
- Add .codex-tmp/ to .gitignore
- Add .workbuddy memory files to .gitignore
- Add frontend/admin/coverage/ to .gitignore
- Add SENIOR_DEV_REVIEW_2026-04-10.md review document

.gitignore

@@ -75,3 +75,18 @@ uploads/avatars/*
 
 # Backup temp
 backup_temp/
+
+# SQLite temp files
+sub2api
+sub2api-shm
+sub2api-wal
+
+# Codex temp
+.codex-tmp/
+
+# Workbuddy memory (local AI memory, not project files)
+.workbuddy/memory/
+.workbuddy/expert-history.json
+
+# Test coverage output
+frontend/admin/coverage/