fix(web): SSR calls use cluster-internal backend URL to bypass nginx timeout

All serverFetch calls were going to https://api.marktvogt.de (public
gateway), creating a second nginx hop for every SSR operation. Slow LLM
calls (merge-plan, research-plan) hit the 60s proxy_read_timeout.

- Add PRIVATE_API_BASE_URL=http://marktvogt-backend to web Helm config
- serverFetch now builds SERVER_API_BASE from PRIVATE_API_BASE_URL at
  runtime (falls back to PUBLIC_API_BASE_URL when not set)
- apiFetch accepts optional baseURL param; client-side calls unchanged

web/deploy/helm/values.yaml

@@ -64,6 +64,8 @@ config:
   HOST: "0.0.0.0"
   # Cloudflare Turnstile — read at runtime via $env/dynamic/public
   PUBLIC_TURNSTILE_SITE_KEY: "0x4AAAAAACjLCV-78Ql1oTPz"
+  # Cluster-internal backend URL — SSR calls bypass the public gateway entirely
+  PRIVATE_API_BASE_URL: "http://marktvogt-backend"
 
 nodeSelector: {}
 tolerations: []

web/src/lib/api/client.server.ts

@@ -1,8 +1,14 @@
 import type { Cookies } from '@sveltejs/kit';
+import { env } from '$env/dynamic/private';
+import { PUBLIC_API_BASE_URL } from '$env/static/public';
 import { apiFetch } from './client.js';
 import type { ApiResponse, AuthData } from './types.js';
 import { setAuthCookies } from '$lib/auth/cookies.js';
 
+// Cluster-internal URL bypasses the public gateway (no nginx hop, no 60s timeout).
+// Falls back to PUBLIC_API_BASE_URL if PRIVATE_API_BASE_URL is not set.
+const SERVER_API_BASE = `${env.PRIVATE_API_BASE_URL ?? PUBLIC_API_BASE_URL}/api/v1`;
+
 export async function serverFetch<T>(
 	path: string,
 	cookies: Cookies,
@@ -17,6 +23,7 @@ export async function serverFetch<T>(
 
 	return apiFetch<T>(path, {
 		...init,
+		baseURL: SERVER_API_BASE,
 		headers: {
 			...headers,
 			...init?.headers

web/src/lib/api/client.ts

@@ -16,12 +16,13 @@ export class ApiClientError extends Error {
 
 export async function apiFetch<T>(
 	path: string,
-	init?: RequestInit & { fetch?: typeof globalThis.fetch }
+	init?: RequestInit & { fetch?: typeof globalThis.fetch; baseURL?: string }
 ): Promise<ApiResponse<T>> {
 	const fetchFn = init?.fetch ?? globalThis.fetch;
-	const { fetch: _, ...restInit } = init ?? {};
+	const { fetch: _, baseURL, ...restInit } = init ?? {};
+	const base = baseURL ?? API_BASE;
 
-	const res = await fetchFn(`${API_BASE}${path}`, {
+	const res = await fetchFn(`${base}${path}`, {
 		headers: {
 			'Content-Type': 'application/json',
 			...restInit.headers