fix: chat build syntax errors, disable GitHub cache on Gitea runner

- Fix 3 orphaned function bodies in main.go (handleAdminSchedule,
  handleAdminSystemSummary, probeMediaDurationSeconds) caused by
  insertions that split function headers from bodies
- Remove cache: true from setup-go and cache: npm from setup-node
  (Gitea runner times out 135s trying to reach GitHub cache API)
- Add go vet ./... step replacing placeholder echo
- Remove || echo fallback from lint (tsc --noEmit is working)

.github/MEMORY.md

@@ -0,0 +1,9 @@
+# MEMORY.md
+
+## 2026-08-05: Chat Message Admin + CI/CD + Release 1.0.5
+
+**Completed**: Chat Message Admin, CI/CD, Release 1.0.5 committed + tagged + pushed.
+
+**Bug — nested admin page**: Fixed. Root cause: page HTML files were in `frontend/admin/` (Vite source root). Vite multi-page mode injected scripts/styles into every `.html` entry. `fetch("/admin/dashboard.html")` returned a full self-contained page, injected into `#tab-content-container`, nesting duplicate admin shell. Fix: moved all 9 page files to `frontend/public/admin/` — Vite serves `public/` contents verbatim with no processing. Fetch now returns raw HTML fragment.
+
+**Key lesson**: Page fragments loaded via `fetch()` must live under `public/` in Vite projects. Any `.html` in the project source root gets processed as a multi-page entry.