fix(search): unblock SearXNG 403 — config + headers

SearXNG returned 403 for every query, logging
'X-Forwarded-For nor X-Real-IP header is set!'. Two fixes, both needed:

1. searxng/settings.yml was being overwritten by SearXNG's default
   config in fresh volumes. Explicitly set limiter: false,
   public_instance: false, and move secret_key to env lookup via
   ${SEARXNG_SECRET:-…}. Force a well-known JSON format list.

2. Even with the limiter off, SearXNG's bot detection still nags on
   missing forwarder headers. The Node client now sends
   X-Forwarded-For: 127.0.0.1, X-Real-IP: 127.0.0.1 and Accept: json
   deterministically. Done via a new extraHeaders option on the http
   wrapper.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

searxng/settings.yml

@@ -1,15 +1,31 @@
 use_default_settings: true
+
 server:
-  secret_key: 'dev-secret-change-in-prod'
+  # In production override via env (see docker-compose.prod.yml).
+  secret_key: ${SEARXNG_SECRET:-dev-secret-change-in-prod}
+  # Disables rate limiter + bot detection. This is a private internal service
+  # called only by kochwas — no public exposure, no abuse risk.
   limiter: false
+  public_instance: false
   image_proxy: false
   default_http_headers:
     X-Content-Type-Options: nosniff
     X-Download-Options: noopen
     X-Robots-Tag: noindex, nofollow
+
 search:
   formats:
     - html
     - json
+  safe_search: 0
+  autocomplete: ''
+  default_lang: 'de'
+
 ui:
   default_locale: de
+
+# Quieten engines that fail on cold start and aren't useful here
+enabled_plugins:
+  - 'Hash plugin'
+  - 'Tracker URL remover'
+  - 'Open Access DOI rewrite'

src/lib/server/http.ts

@@ -2,9 +2,10 @@ export type FetchOptions = {
   maxBytes?: number;
   timeoutMs?: number;
   userAgent?: string;
+  extraHeaders?: Record<string, string>;
 };
 
-const DEFAULTS: Required<FetchOptions> = {
+const DEFAULTS: Required<Omit<FetchOptions, 'extraHeaders'>> = {
   maxBytes: 10 * 1024 * 1024,
   timeoutMs: 10_000,
   userAgent: 'Kochwas/0.1'
@@ -57,14 +58,19 @@ async function readBody(
 
 async function doFetch(url: string, opts: FetchOptions): Promise<Response> {
   assertSafeUrl(url);
-  const merged = { ...DEFAULTS, ...opts };
+  const timeoutMs = opts.timeoutMs ?? DEFAULTS.timeoutMs;
+  const userAgent = opts.userAgent ?? DEFAULTS.userAgent;
   const controller = new AbortController();
-  const timer = setTimeout(() => controller.abort(), merged.timeoutMs);
+  const timer = setTimeout(() => controller.abort(), timeoutMs);
+  const headers: Record<string, string> = {
+    'user-agent': userAgent,
+    ...(opts.extraHeaders ?? {})
+  };
   try {
     const res = await fetch(url, {
       signal: controller.signal,
       redirect: 'follow',
-      headers: { 'user-agent': merged.userAgent }
+      headers
     });
     if (!res.ok) throw new Error(`HTTP ${res.status} for ${url}`);
     return res;
@@ -74,9 +80,9 @@ async function doFetch(url: string, opts: FetchOptions): Promise<Response> {
 }
 
 export async function fetchText(url: string, opts: FetchOptions = {}): Promise<string> {
-  const merged = { ...DEFAULTS, ...opts };
+  const maxBytes = opts.maxBytes ?? DEFAULTS.maxBytes;
-  const res = await doFetch(url, merged);
+  const res = await doFetch(url, opts);
-  const { data } = await readBody(res, merged.maxBytes);
+  const { data } = await readBody(res, maxBytes);
   return new TextDecoder('utf-8').decode(data);
 }
 
@@ -84,8 +90,8 @@ export async function fetchBuffer(
   url: string,
   opts: FetchOptions = {}
 ): Promise<{ data: Uint8Array; contentType: string | null }> {
-  const merged = { ...DEFAULTS, ...opts };
+  const maxBytes = opts.maxBytes ?? DEFAULTS.maxBytes;
-  const res = await doFetch(url, merged);
+  const res = await doFetch(url, opts);
-  const { data } = await readBody(res, merged.maxBytes);
+  const { data } = await readBody(res, maxBytes);
   return { data, contentType: res.headers.get('content-type') };
 }

src/lib/server/search/searxng.ts

@@ -96,7 +96,16 @@ export async function searchWeb(
   endpoint.searchParams.set('format', 'json');
   endpoint.searchParams.set('language', 'de');
 
-  const body = await fetchText(endpoint.toString(), { timeoutMs: 15_000 });
+  const body = await fetchText(endpoint.toString(), {
+    timeoutMs: 15_000,
+    // SearXNG's bot detection complains without these; we are the only caller
+    // and we're not a bot, so satisfy the check deterministically.
+    extraHeaders: {
+      'X-Forwarded-For': '127.0.0.1',
+      'X-Real-IP': '127.0.0.1',
+      Accept: 'application/json'
+    }
+  });
   let parsed: SearxngResponse;
   try {
     parsed = JSON.parse(body) as SearxngResponse;