searxng: wire paid Kagi engine with deploy-time key rendering

The stock SearXNG image ships a native kagi engine; enabling it needs an
API key that must never enter git, and SearXNG does not expand env vars
in settings.yml (the live secret_key literally was '${SEARXNG_SECRET}'
until now — the app tolerated the placeholder string silently).

- settings.yml: kagi engine enabled (weight 2, kg shortcut, paging off so
  exactly one API credit per aggregated query, timeout 8.0 vs 5.0 scrapers
  so a slow paid query is not a wasted credit); api_key stays ${KAGI_API_KEY}.
- new scripts/searxng-render-settings.py: deploy-time renderer, allowlisted
  to KAGI_API_KEY/SEARXNG_SECRET/SEARXNG_BASE_URL, fails the deploy loudly
  on an unresolvable placeholder, idempotent on redeploys.
- deploy-remote.sh copy_searxng_config runs the renderer against
  /opt/searxng/.env after copying settings.yml into /opt/searxng/config.
- KAGI_API_KEY placeholder added to dankclaw/.env.example (real key staged
  into the host-side /opt/searxng/.env, mode 600, out of band).
- bats: engine wiring, renderer substitution, loud-failure, deployer seam.
- docs: SearXNG.md Kagi section + renderer law; Providers.md carve-out on
  the no-credentials policy (paid engine acceptable when bounded + ordered).

Verified live on dankclaw: direct API probe via the gluetun netns (200,
data.search[] shape), then an aggregated query returned 29/29 results
tagged kagi, zero unresponsive engines.

serverAppConfigs-docs/Dankclaw/SearXNG.md

@@ -60,8 +60,8 @@ Deploy with `scripts/deploy-searxng-quadlet.sh dankclaw`. It copies the units, d
 ```yaml
 use_default_settings: true
 server:
-  secret_key: "${SEARXNG_SECRET}"   # from .env
-  base_url: "${SEARXNG_BASE_URL}"  # resolves to http://192.168.0.143:8081/
+  secret_key: "${SEARXNG_SECRET}"   # rendered at deploy by scripts/searxng-render-settings.py
+  base_url: "${SEARXNG_BASE_URL}"   # same renderer; SearXNG does NOT expand env vars itself
   limiter: true
   method: "POST"
 
@@ -90,8 +90,16 @@ engines:
   - name: duckduckgo
     disabled: false
     weight: 2
-    paging: false
-    timeout: 5.0
+  - name: kagi
+    engine: kagi
+    categories: [general, web]
+    shortcut: kg
+    api_key: "${KAGI_API_KEY}"      # rendered at deploy from /opt/searxng/.env
+    kagi_categ: search
+    disabled: false
+    weight: 2
+    paging: false                  # one API credit per aggregated query
+    timeout: 8.0
   - name: google cse
     disabled: true
   - name: brave
@@ -168,10 +176,39 @@ root cause, the suspend-model table, the `engines:` config, and the
   LAN by construction (no public route to the LAN IP). No second agent-only
   instance is needed; a duplicate would double upstream request volume from the
   same rate-sensitive VPN exit IP for zero benefit.
-- The config file is root-owned (uid of the rootless podman namespace). Update it with a one-off `sudo cp`, then run `systemctl --user restart searxng.service` to reload.
+- The config file is root-owned (uid of the rootless podman namespace). The
+  official path is `deploy.sh --service searxng`: it copies the repo settings
+  and renders the `${VAR}` placeholders via `scripts/searxng-render-settings.py`
+  from `/opt/searxng/.env`. A hotfix can still hand-copy with `sudo cp`, but
+  remember the renderer: an unrendered copy silently serves the literal
+  placeholders (before 2026-09-26 the live `secret_key` literally was
+  `"${SEARXNG_SECRET}"` and nobody noticed).
 - `base_url` must match the public address or proxy rewrites break.
 - Keep the valkey cache container on the same podman network as searxng.
 
+
+## Kagi (paid API engine)
+
+Added 2026-09-26 (user-ordered). The stock SearXNG image ships a native
+`kagi` engine module (`searx/engines/kagi.py`); it authenticates with
+`Authorization: Bearer <key>` against `POST https://kagi.com/api/v1/search`.
+
+- **Enabled**: `weight: 2` alongside bing/duckduckgo, categories
+  `[general, web]`, shortcut `kg`, `kagi_categ: search`.
+- **Cost control**: `paging: false` — exactly one API credit per aggregated
+  query; `timeout: 8.0` so a slow paid query is not wasted (scrapers use 5.0).
+- **Key handling**: the repo file keeps `api_key: "${KAGI_API_KEY}"`;
+  `deploy-remote.sh` bakes the real key into the live settings.yml via
+  `scripts/searxng-render-settings.py`, reading `/opt/searxng/.env`
+  (dank-owned, mode 600). The key never enters git and never appears in any
+  process argv. SearXNG itself does NOT expand env vars in settings.yml —
+  without the renderer the engine fails `setup()` and is dropped at load.
+- **Immune to the VPN-exit-IP problem**: Kagi authenticates, so it does not
+  care about the shared Gluetun exit IP reputation (see [[SearXNG Providers]]).
+- **Verified live 2026-09-26**: direct API probe through the gluetun netns
+  (200, `data.search[]` shape), then a live aggregated query returned
+  29/29 results tagged `kagi`, zero unresponsive engines.
+
 ## See Also
 
 - [[Dankclaw Stack]]