feat(security): add CSRF protection for all state-changing API routes

- Synchronizer token stored in session; GET /auth/csrf to obtain it
- csrfProtection middleware requires X-CSRF-Token on non-safe methods
- customFetch injects the header via setCsrfTokenGetter
- toolrate boot loads token; reload after local login (session regenerate)
- OpenAPI GET /auth/csrf + CsrfToken schema, orval regenerated

artifacts/api-server/src/middleware/csrf.ts

@@ -0,0 +1,25 @@
+import crypto from "node:crypto";
+import type { Request, Response, NextFunction } from "express";
+
+const SAFE_METHODS = new Set(["GET", "HEAD", "OPTIONS", "TRACE"]);
+
+export function getCsrfToken(req: Request): string {
+  if (!req.session.csrfToken) {
+    req.session.csrfToken = crypto.randomBytes(24).toString("hex");
+  }
+  return req.session.csrfToken;
+}
+
+export function csrfProtection(req: Request, res: Response, next: NextFunction): void {
+  if (SAFE_METHODS.has(req.method.toUpperCase())) {
+    next();
+    return;
+  }
+  const provided = req.headers["x-csrf-token"];
+  const token = getCsrfToken(req);
+  if (typeof provided === "string" && provided && provided === token) {
+    next();
+    return;
+  }
+  res.status(403).json({ error: "CSRF token missing or invalid" });
+}

artifacts/api-server/src/routes/auth.ts

@@ -8,6 +8,7 @@ import { logger } from "../lib/logger";
 import { writeAuditLog } from "../lib/audit";
 import { loginRateLimit, passwordRateLimit } from "../lib/rate-limit";
 import { getEntitlements, requireFeature } from "../middleware/feature";
+import { getCsrfToken } from "../middleware/csrf";
 
 const router: IRouter = Router();
 
@@ -109,6 +110,10 @@ router.get("/auth/mode", (_req, res): void => {
   res.json({ mode: isOidcConfigured() ? "oidc" : "local" });
 });
 
+router.get("/auth/csrf", (req, res): void => {
+  res.json({ token: getCsrfToken(req) });
+});
+
 router.post("/auth/login", loginRateLimit, async (req, res): Promise<void> => {
   if (isOidcConfigured()) {
     res.status(400).json({ error: "Use OIDC login when Keycloak is configured." });

artifacts/api-server/src/routes/index.ts

@@ -8,9 +8,12 @@ import usersRouter from "./users";
 import auditRouter from "./audit";
 import costsRouter from "./costs";
 import adminRouter from "./admin";
+import { csrfProtection } from "../middleware/csrf";
 
 const router: IRouter = Router();
 
+router.use(csrfProtection);
+
 router.use(authRouter);
 router.use(healthRouter);
 router.use(toolsRouter);

artifacts/api-server/src/types/session.d.ts

@@ -14,5 +14,6 @@ declare module "express-session" {
     codeVerifier?: string;
     returnTo?: string;
     oidcState?: string;
+    csrfToken?: string;
   }
 }