security: address assessment findings and bump to v2026.3.11

- C1: Disable Swagger UI in production (env gate)
- M1+M2: Add Helmet.js for security headers (CSP, X-Frame-Options,
  X-Content-Type-Options, Referrer-Policy) and remove X-Powered-By
- H2: Add @nestjs/throttler rate limiting (5 req/min on login/register)
- M4: Remove orgSchema from JWT payload and client-side storage;
  tenant middleware now resolves schema from orgId via cached DB lookup
- L1: Fix Chatwoot user identification (read from auth store on ready)
- Remove schemaName from frontend Organization type and UI displays

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

backend/src/modules/auth/strategies/jwt.strategy.ts

@@ -18,7 +18,6 @@ export class JwtStrategy extends PassportStrategy(Strategy) {
       sub: payload.sub,
       email: payload.email,
       orgId: payload.orgId,
-      orgSchema: payload.orgSchema,
       role: payload.role,
       isSuperadmin: payload.isSuperadmin || false,
       impersonatedBy: payload.impersonatedBy || null,