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.

server/internal/shared/auth/context_test.go

@@ -0,0 +1,36 @@
+package auth
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestWithActorAndFromCtx(t *testing.T) {
+	actor := Actor{UserID: 1, TenantID: 10, Role: "editor"}
+	ctx := WithActor(context.Background(), actor)
+
+	got, ok := ActorFromCtx(ctx)
+	assert.True(t, ok)
+	assert.Equal(t, actor, got)
+}
+
+func TestActorFromCtxMissing(t *testing.T) {
+	_, ok := ActorFromCtx(context.Background())
+	assert.False(t, ok)
+}
+
+func TestMustActorPanics(t *testing.T) {
+	assert.Panics(t, func() {
+		MustActor(context.Background())
+	})
+}
+
+func TestMustActorReturns(t *testing.T) {
+	actor := Actor{UserID: 5, TenantID: 20, Role: "tenant_admin"}
+	ctx := WithActor(context.Background(), actor)
+
+	got := MustActor(ctx)
+	assert.Equal(t, actor, got)
+}