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/app/actions/ai-actions.ts

@@ -94,9 +94,7 @@ export interface RefactorParagraphResponse {
  * This feature will analyze all user notes with embeddings to find
  * connections with cosine similarity > 0.75 and provide proactive insights.
  */
-export interface GenerateMemoryEchoRequest {
-  // No params - uses current user session
-}
+export type GenerateMemoryEchoRequest = Record<string, never>
 
 export interface MemoryEchoInsight {
   note1Id: string