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/llm/client.go

@@ -0,0 +1,53 @@
+package llm
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/geo-platform/tenant-api/internal/shared/config"
+)
+
+var ErrNotConfigured = errors.New("llm provider is not configured")
+
+type GenerateRequest struct {
+	Prompt string
+}
+
+type GenerateResult struct {
+	Content string
+	Model   string
+}
+
+type Client interface {
+	Validate() error
+	Generate(ctx context.Context, req GenerateRequest, onDelta func(string)) (*GenerateResult, error)
+}
+
+func New(cfg config.LLMConfig) Client {
+	provider := strings.ToLower(strings.TrimSpace(cfg.Provider))
+	switch provider {
+	case "", "disabled":
+		return disabledClient{reason: "llm provider is disabled"}
+	case "ark":
+		return NewArkClient(cfg)
+	default:
+		return disabledClient{reason: fmt.Sprintf("unsupported llm provider %q", cfg.Provider)}
+	}
+}
+
+type disabledClient struct {
+	reason string
+}
+
+func (c disabledClient) Validate() error {
+	if c.reason == "" {
+		c.reason = "missing LLM configuration"
+	}
+	return fmt.Errorf("%w: %s", ErrNotConfigured, c.reason)
+}
+
+func (c disabledClient) Generate(context.Context, GenerateRequest, func(string)) (*GenerateResult, error) {
+	return nil, c.Validate()
+}