chore(ci): migrate to Gitea local CI, disable GitHub Actions

- Add .gitea/workflows/ci.yml for self-hosted Gitea runner
- Disable .github/workflows/ci.yml (GitHub billing blocked)

.gitea/workflows/ci.yml

@@ -0,0 +1,60 @@
+name: CI — ChronoMind
+
+on:
+  push:
+    branches: [main]
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  COMMON_PLAT: /Users/sd9235/code/mygh/learning_ai_common_plat
+  DB_PROVIDER: memory
+  JWT_SECRET: ci-test-secret-at-least-32-characters-long
+  NEXT_TELEMETRY_DISABLED: '1'
+
+jobs:
+  backend:
+    name: Backend — typecheck + test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build @bytelyst/* packages
+        working-directory: ${{ env.COMMON_PLAT }}
+        run: pnpm install --frozen-lockfile && pnpm build
+
+      - name: Install workspace dependencies
+        run: pnpm install
+
+      - name: Backend typecheck
+        run: pnpm --filter @chronomind/backend run typecheck
+
+      - name: Backend tests
+        run: pnpm --filter @chronomind/backend run test
+
+  web:
+    name: Web — typecheck + lint + test + build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build @bytelyst/* packages
+        working-directory: ${{ env.COMMON_PLAT }}
+        run: pnpm install --frozen-lockfile && pnpm build
+
+      - name: Install workspace dependencies
+        run: pnpm install
+
+      - name: Web typecheck
+        run: pnpm --filter web run typecheck
+
+      - name: Web lint
+        run: pnpm --filter web run lint
+
+      - name: Web test
+        run: pnpm --filter web run test
+
+      - name: Web build
+        run: pnpm --filter web run build