feat: auth service + security audit fixes + cleanup legacy services

Major changes:
- Add auth-svc: JWT auth, register/login/refresh, password reset
- Add auth UI: modals, pages (/login, /register, /forgot-password)
- Add usage tracking (usage_metrics table, daily limits)
- Add tiered rate limiting (free/pro/business)
- Add LLM usage limits per tier

Security fixes:
- All repos now require userID for Update/Delete operations
- JWT middleware in chat-svc, llm-svc, agent-svc, discover-svc
- ErrNotFound/ErrForbidden errors for proper access control

Cleanup:
- Remove legacy TypeScript services/ directory
- Remove computer-svc (to be reimplemented)
- Remove old deploy/docker configs

New files:
- backend/cmd/auth-svc/main.go
- backend/internal/auth/{types,repository}.go
- backend/internal/usage/{types,repository}.go
- backend/pkg/middleware/{llm_limits,ratelimit_tiered}.go
- backend/webui/src/components/auth/*
- backend/webui/src/app/(auth)/*

Made-with: Cursor

backend/internal/db/space_repo.go

@@ -139,7 +139,7 @@ func (r *SpaceRepository) GetByUserID(ctx context.Context, userID string) ([]*Sp
 	return spaces, nil
 }
 
-func (r *SpaceRepository) Update(ctx context.Context, s *Space) error {
+func (r *SpaceRepository) Update(ctx context.Context, s *Space, userID string) error {
 	settingsJSON, _ := json.Marshal(s.Settings)
 
 	query := `
@@ -147,17 +147,31 @@ func (r *SpaceRepository) Update(ctx context.Context, s *Space) error {
 		SET name = $2, description = $3, icon = $4, color = $5, 
 			custom_instructions = $6, default_focus_mode = $7, default_model = $8,
 			is_public = $9, settings = $10, updated_at = NOW()
-		WHERE id = $1
+		WHERE id = $1 AND user_id = $11
 	`
-	_, err := r.db.db.ExecContext(ctx, query,
+	result, err := r.db.db.ExecContext(ctx, query,
 		s.ID, s.Name, s.Description, s.Icon, s.Color,
 		s.CustomInstructions, s.DefaultFocusMode, s.DefaultModel,
-		s.IsPublic, settingsJSON,
+		s.IsPublic, settingsJSON, userID,
 	)
-	return err
+	if err != nil {
+		return err
+	}
+	rows, _ := result.RowsAffected()
+	if rows == 0 {
+		return ErrNotFound
+	}
+	return nil
 }
 
-func (r *SpaceRepository) Delete(ctx context.Context, id string) error {
-	_, err := r.db.db.ExecContext(ctx, "DELETE FROM spaces WHERE id = $1", id)
-	return err
+func (r *SpaceRepository) Delete(ctx context.Context, id, userID string) error {
+	result, err := r.db.db.ExecContext(ctx, "DELETE FROM spaces WHERE id = $1 AND user_id = $2", id, userID)
+	if err != nil {
+		return err
+	}
+	rows, _ := result.RowsAffected()
+	if rows == 0 {
+		return ErrNotFound
+	}
+	return nil
 }