feat: add CI pipeline with ESLint, refactor deploy with rollback + Telegram

- Add eslint.config.mjs (flat config, eslint-config-next@16 + TypeScript)
- Add .gitea/workflows/ci.yaml (lint, test:unit, build on all branches)
- Refactor deploy.yaml: needs: [ci] gate, Docker rollback tag, Telegram notifications
- Fix 3 pre-existing lint errors (empty interfaces, ts-ignore, require imports)

memento-note/next.config.ts

@@ -52,7 +52,7 @@ const nextConfig: NextConfig = {
   reactStrictMode: false,
 
   // Allow development origins for HMR and Dev Server access
-  // @ts-ignore - Some NextConfig versions might require this in experimental
+  // @ts-expect-error - Some NextConfig versions might require this in experimental
   allowedDevOrigins: ['192.168.1.83'],
 };