fix: prevent Invalid URL crash when APP_URL lacks a protocol (#972)

* fix: prevent Invalid URL crash when APP_URL lacks a protocol (issue #970)

- Add getMcpSafeUrl() to notifications.ts: wraps getAppUrl() and
  guarantees a result that satisfies the MCP SDK's checkIssuerUrl
  requirement (https:// or http://localhost). Non-HTTPS, non-localhost
  URLs fall back to http://localhost:{PORT} instead of propagating an
  "Issuer URL must be HTTPS" error.
- Switch app.ts, mcp/index.ts, mcp/oauthProvider.ts, and oauthService.ts
  to import getMcpSafeUrl instead of getAppUrl for all MCP resource URL
  construction, so a misconfigured APP_URL never crashes the metadata
  router initialisation.
- Restrict the SDK metadata router middleware to /.well-known/* paths
  only. Previously it was invoked on every request; in production the
  lazy getMetaRouter() init ran on GET / and threw "Invalid URL" when
  APP_URL had no scheme, returning 500 for every page load.
- Log a startup warning when APP_URL is set but not usable, and include
  the resolved App URL in the startup banner so operators can confirm
  the correct value at a glance.
- Update oauth.test.ts mock to target notifications.getMcpSafeUrl.

* fix: show getAppUrl in banner and add two separate APP_URL startup checks

- Banner now displays getAppUrl() (the resolved app URL) rather than
  getMcpSafeUrl() so operators see the actual configured value
- Two independent startup warnings after the banner when APP_URL is set:
  1. whether APP_URL is a valid URL (parseable by new URL())
  2. whether APP_URL is MCP-safe (https:// or http://localhost)
- Fix getMcpSafeUrl() fallback port to use Number(PORT) || 3001,
  consistent with how index.ts parses PORT

* fix: update oidc.ts to import getAppUrl from notifications

server/src/mcp/index.ts

@@ -11,7 +11,7 @@ import { registerResources } from './resources';
 import { registerTools } from './tools';
 import { McpSession, sessions, revokeUserSessions, revokeUserSessionsForClient } from './sessionManager';
 import { writeAudit, getClientIp } from '../services/auditLog';
-import { getAppUrl } from '../services/oidcService';
+import { getMcpSafeUrl } from '../services/notifications';
 
 export { revokeUserSessions, revokeUserSessionsForClient };
 
@@ -153,7 +153,7 @@ const sessionSweepInterval = setInterval(() => {
 sessionSweepInterval.unref();
 
 function setAuthChallenge(res: Response, error = 'invalid_token'): void {
-  const base = (getAppUrl() || '').replace(/\/+$/, '');
+  const base = (getMcpSafeUrl() || '').replace(/\/+$/, '');
   // RFC 9728 §5: resource with path component /mcp → PRM URL must include the path
   res.set('WWW-Authenticate',
       `Bearer realm="TREK MCP", resource_metadata="${base}/.well-known/oauth-protected-resource/mcp", error="${error}"`);
@@ -183,7 +183,7 @@ function verifyToken(authHeader: string | undefined): VerifyTokenResult | null {
     if (!result) return null;
     // RFC 8707: audience must always match this resource endpoint.
     // Pre-audit tokens with audience=null are revoked by the SEC-H6 migration.
-    const expected = `${(getAppUrl() || '').replace(/\/+$/, '')}/mcp`;
+    const expected = `${(getMcpSafeUrl() || '').replace(/\/+$/, '')}/mcp`;
     if (result.audience !== expected) return null;
     return { user: result.user, scopes: result.scopes, clientId: result.clientId, isStaticToken: false };
   }

server/src/mcp/oauthProvider.ts

@@ -16,7 +16,7 @@ import {
     getUserByAccessToken,
 } from '../services/oauthService';
 import { ALL_SCOPES } from './scopes';
-import { getAppUrl } from '../services/oidcService';
+import { getMcpSafeUrl } from '../services/notifications';
 import { writeAudit } from '../services/auditLog';
 
 // ---------------------------------------------------------------------------
@@ -125,7 +125,7 @@ export const trekOAuthProvider: OAuthServerProvider = {
 
     // Redirects browser to the SPA consent page with OAuth params forwarded.
     async authorize(client: OAuthClientInformationFull, params: AuthorizationParams, res: Response): Promise<void> {
-        const mcpResource = `${(getAppUrl() || '').replace(/\/+$/, '')}/mcp`;
+        const mcpResource = `${getMcpSafeUrl().replace(/\/+$/, '')}/mcp`;
         const resource = params.resource ? params.resource.href.replace(/\/+$/, '') : mcpResource;
 
         if (resource !== mcpResource) {