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/migrations/20260331100023_create_brand_question_versions.up.sql

@@ -0,0 +1,11 @@
+CREATE TABLE brand_question_versions (
+    id            BIGSERIAL PRIMARY KEY,
+    question_id   BIGINT NOT NULL REFERENCES brand_questions(id),
+    question_text TEXT NOT NULL,
+    question_hash VARCHAR(64) NOT NULL,
+    version_no    INT NOT NULL,
+    is_active     BOOLEAN NOT NULL DEFAULT true,
+    created_at    TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    CONSTRAINT uk_question_version_no UNIQUE (question_id, version_no)
+);
+CREATE INDEX idx_question_hash ON brand_question_versions(question_hash);