fix(portal): security hardening for pilot readiness

- C1: Rewrite /api/usage to resolve teamId server-side from tenant CR;
  customers can no longer pass arbitrary teamId (IDOR fix)
- C2: Remove POST /api/tenants — tenants are only created via admin
  approval flow
- H1: Validate packages against catalog, workspaceFiles against allowlist,
  and field lengths in PATCH /api/tenants/[name]
- H2: Remove full ZITADEL profile claims logging from JWT callback
- H3: Add safeError() utility; sanitize all error responses to clients,
  toggle raw errors via PORTAL_DEBUG_ERRORS=true
- H4/H5: Escape HTML entities in all email templates (contactName,
  companyName, adminNotes)

src/app/api/tenants/route.ts

@@ -1,7 +1,6 @@
 import { NextResponse } from "next/server";
 import { getSessionUser } from "@/lib/session";
-import { listTenants, getTenant, createTenant } from "@/lib/k8s";
-import type { PiecedTenantSpec } from "@/types";
+import { listTenants } from "@/lib/k8s";
 
 export async function GET() {
   const user = await getSessionUser();
@@ -20,37 +19,3 @@ export async function GET() {
   );
   return NextResponse.json(own);
 }
-
-export async function POST(request: Request) {
-  const user = await getSessionUser();
-  if (!user)
-    return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
-  if (!user.isPlatform && !user.roles.includes("owner")) {
-    return NextResponse.json({ error: "Forbidden" }, { status: 403 });
-  }
-
-  const body = (await request.json()) as {
-    name: string;
-    spec: PiecedTenantSpec;
-  };
-
-  if (!/^[a-z0-9][a-z0-9-]*[a-z0-9]$/.test(body.name) || body.name.length > 63) {
-    return NextResponse.json(
-      { error: "Invalid tenant name: lowercase alphanumeric and hyphens, 2-63 chars" },
-      { status: 400 }
-    );
-  }
-
-  const existing = await getTenant(body.name);
-  if (existing) {
-    return NextResponse.json(
-      { error: "Tenant already exists" },
-      { status: 409 }
-    );
-  }
-
-  const tenant = await createTenant(body.name, body.spec, {
-    "pieced.ch/zitadel-org-id": user.orgId,
-  });
-  return NextResponse.json(tenant, { status: 201 });
-}