v1.11.8: web_search + web_fetch tools via SearXNG

Adds two new tools registered through the existing ALL_TOOLS registry:
  - web_search hits SearXNG's JSON API (Fathom, internal Tailscale URL,
    no auth) and returns top results
  - web_fetch retrieves a URL's text content, gated by isPublicUrl
    (url_guard.ts) which blocks loopback / RFC1918 / Tailscale CGNAT /
    link-local / .local / .internal / non-http schemes

Both tools are opt-in via the existing session.web_search_enabled flag
(plumbed in v1.9, activated here). Default off. UI labels updated to
"Enable web search and fetch" / "Web search and fetch" since fetch joins
the same store. Counts against the v1.8.2 per-turn budget; covered by
the v1.11.6 doom-loop guard.

Native Node 20 fetch — no new prod dep. HTML stripping via regex (script
and style content elided wholesale). 5MB body cap, 15s fetch timeout,
8000-char default output, 32000-char cap.

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

.env.example

@@ -6,3 +6,7 @@ PROJECT_ROOT_WHITELIST=/opt
 BOOTSTRAP_ROOT=/opt/projects
 DEFAULT_MODEL=qwen3.6-35b-a3b-mxfp4
 POSTGRES_PASSWORD=CHANGE_ME
+# v1.11.8: SearXNG JSON endpoint for the web_search / web_fetch tools.
+# Internal Tailscale address that bypasses Authelia. Override if you
+# point BooCode at a different SearXNG instance.
+SEARXNG_URL=http://100.114.205.53:8888