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)

.gitea/workflows/ci.yaml

@@ -0,0 +1,43 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - main
+      - "*"
+  pull_request:
+    branches:
+      - main
+
+jobs:
+  ci:
+    name: Lint, Test & Build
+    runs-on: ubuntu-24.04
+    defaults:
+      run:
+        working-directory: memento-note
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node 22
+        uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+          cache: "npm"
+          cache-dependency-path: memento-note/package-lock.json
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Generate Prisma client
+        run: npx prisma generate
+
+      - name: Lint
+        run: npm run lint -- --max-warnings 999
+
+      - name: Unit tests
+        run: npm run test:unit
+
+      - name: Build
+        run: npm run build