feat: add Gitea Actions CI workflow

Includes lint/typechecking (svelte-check) and frontend build stages,
triggered on push/PR to main/master/develop branches.

.gitea/workflows/ci.yaml

@@ -0,0 +1,71 @@
+name: CI
+run-name: CI (${{ gitea.ref_name }})
+
+on:
+  push:
+    branches: [main, master, develop]
+  pull_request:
+    branches: [main, master]
+
+jobs:
+  lint-and-typecheck:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Cache node_modules
+        uses: actions/cache@v4
+        with:
+          path: node_modules
+          key: ${{ runner.os }}-node-${{ hashFiles('package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Svelte check (type checking)
+        run: npm run check
+
+      - name: Lint (if configured)
+        run: npx svelte-check --tsconfig ./tsconfig.json
+        continue-on-error: true
+
+  build-frontend:
+    runs-on: ubuntu-latest
+    needs: [lint-and-typecheck]
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+
+      - name: Cache node_modules
+        uses: actions/cache@v4
+        with:
+          path: node_modules
+          key: ${{ runner.os }}-node-${{ hashFiles('package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build frontend (Vite)
+        run: npx vite build
+
+      - name: Upload dist artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: frontend-dist
+          path: dist/
+          retention-days: 7