refactor: remove schema-manager and tenantSchema backward compat

Delete schema-manager.ts (replaced by TenantConnectionManager).
Remove deprecated tenantSchema from Express Request interface.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/api/src/middlewares/tenant.middleware.ts

@@ -6,7 +6,6 @@ declare global {
   namespace Express {
     interface Request {
       tenantPool?: Pool;
-      tenantSchema?: string; // @deprecated - use tenantPool instead
       viewingTenantId?: string;
     }
   }
@@ -47,12 +46,7 @@ export async function tenantMiddleware(req: Request, res: Response, next: NextFu
       req.viewingTenantId = viewedTenant.id;
     }
 
-    // New pool-based approach
     req.tenantPool = tenantDb.getPool(tenantId, databaseName);
-
-    // Backward compat: tenantSchema still used by controllers until Task 8 migration
-    req.tenantSchema = databaseName;
-
     next();
   } catch (error) {
     console.error('[TenantMiddleware] Error:', error);