feat: add tenant and user management with migrations, handlers, and tests

- Implemented tenant and user management features including:
  - Tenant creation and management with associated migrations.
  - User creation and management with associated migrations.
  - Tenant membership management with associated migrations.
  - Platform user roles management with associated migrations.
  - Quota management with associated migrations.
  - Article and template management with associated migrations.
- Added HTTP handlers for templates and workspaces.
- Created tests for protected and public routes.
- Introduced a script to check tenant scope in SQL queries.
- Documented task plan for backend completion and frontend foundation.

.github/workflows/backend-ci.yml

@@ -0,0 +1,56 @@
+name: Backend CI
+
+on:
+  push:
+    paths:
+      - "server/**"
+      - ".github/workflows/backend-ci.yml"
+  pull_request:
+    paths:
+      - "server/**"
+      - ".github/workflows/backend-ci.yml"
+
+permissions:
+  contents: read
+
+jobs:
+  backend:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: server
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Setup Go
+        uses: actions/setup-go@v5
+        with:
+          go-version-file: server/go.mod
+          cache-dependency-path: server/go.sum
+
+      - name: Add Go bin to PATH
+        run: echo "$(go env GOPATH)/bin" >> "$GITHUB_PATH"
+
+      - name: Install sqlc
+        run: go install github.com/sqlc-dev/sqlc/cmd/sqlc@v1.30.0
+
+      - name: Generate sqlc code
+        run: make sqlc-generate
+
+      - name: Verify generated code is committed
+        run: git diff --exit-code -- internal/tenant/repository/generated
+
+      - name: Check tenant SQL scope guard
+        run: make tenant-scope-guard
+
+      - name: Run tests
+        run: make test
+
+      - name: Run golangci-lint
+        uses: golangci/golangci-lint-action@v6
+        with:
+          version: v1.59.1
+          working-directory: server
+          args: ./...