PWA, one send/stop button, audio in and out, web search as a tool

Four pieces of work.

**Installable.** A manifest carrying the instance name, PWA icons rasterised
from the existing mark at design time, a service worker and a themed offline
page. The worker caches the shell only and bails out on /api/, /auth/, /admin/
and anything accepting text/event-stream -- passing a reply stream through a
worker turns it into one delivery at the end, or nothing. It is served from
GET /sw.js rather than the static mount because a worker's scope is the path it
came from.

**Send and Stop are one button.** They were two, and the hidden one was never
hidden: `.btn` is display: inline-flex, which outranks the browser's own
`[hidden] { display: none }`, so Stop sat permanently beside Send. app.css now
forces the attribute to win -- every control toggled with `hidden` depended on
that -- and the composer renders one button carrying both icons, with ui.js
flipping data-composer-action and the type with it.

**Audio.** Speech to text and text to speech against any OpenAI-shaped
/v1/audio/* endpoint: dictate into the composer, have a reply read out.
Instance settings in Admin, per-reader overrides in Settings, with the voice
list discovered from the server where it offers one. Recorded audio is capped
and never written to disk -- it is not an attachment, it has no owner, and
nothing would ever sweep it.

**Web search, as a tool.** This is the tool loop PLAN.md described as the real
work: one reply is now a bounded sequence of requests rather than one. The model
asks, the tool runs, the result goes back and it is asked again, up to three
rounds. Providers are DuckDuckGo (no setup), SearXNG and Firecrawl.

Two decisions worth stating. Tools are only offered to models flagged `tools`,
because an endpoint without support rejects the whole request rather than
ignoring the array -- the same reason images only reach models flagged
`vision`. And tool results are not replayed as context on the next turn, for the
same reasons reasoning is not: the answer already contains what the model made
of them, and replaying stale results into every later request wastes the window
and reliably sends a small model into a search loop. The sources stay visible in
the transcript instead.

Search results are untrusted third-party text and are treated as such: escaped,
and only http/https URLs rendered as links.

338 tests, ruff clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lembas/api/admin_search.py

@@ -0,0 +1,110 @@
+"""Web search administration: which provider, and how to reach it."""
+
+from __future__ import annotations
+
+import logging
+
+from fastapi import APIRouter, Form, Request, Response, status
+from fastapi.responses import RedirectResponse
+
+from lembas.api.deps import AdminUser, Db
+from lembas.services import search as search_service
+from lembas.services import settings_store
+from lembas.services.crypto import UNCHANGED_SENTINEL, decrypt, keep_or_replace, mask
+from lembas.services.search.base import SearchError
+from lembas.web.templating import render
+
+log = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/admin/search", tags=["admin-search"])
+
+SAFESEARCH = ("off", "moderate", "strict")
+
+
+@router.get("")
+async def search_page(request: Request, db: Db, user: AdminUser, saved: bool = False):
+    values = settings_store.search(db)
+    return render(
+        request,
+        "admin/search.html",
+        {
+            "values": values,
+            "providers": search_service.PROVIDERS,
+            # Keyed by provider so the form can show an install hint against
+            # the one that needs it, without the template knowing why.
+            "problems": {
+                p.key: search_service.availability(p.key) for p in search_service.PROVIDERS
+            },
+            "safesearch_options": SAFESEARCH,
+            "masked": mask(decrypt(values.get("firecrawl_api_key_encrypted") or "")),
+            "unchanged": UNCHANGED_SENTINEL,
+            "saved": saved,
+        },
+    )
+
+
+@router.post("")
+async def save_search(
+    db: Db,
+    user: AdminUser,
+    enabled: bool = Form(False),
+    provider: str = Form("ddgs"),
+    max_results: int = Form(5),
+    region: str = Form("wt-wt"),
+    safesearch: str = Form("moderate"),
+    searxng_base_url: str = Form(""),
+    firecrawl_base_url: str = Form(""),
+    firecrawl_api_key: str = Form(""),
+    timeout: float = Form(20.0),
+) -> Response:
+    current = settings_store.search(db)
+    known = {p.key for p in search_service.PROVIDERS}
+
+    settings_store.update(
+        db,
+        {
+            "enabled": enabled,
+            "provider": provider if provider in known else "ddgs",
+            # An upper bound on what any single search may put in the prompt.
+            # Twenty results is already more than a model reads carefully.
+            "max_results": min(max(max_results, 1), 20),
+            "region": region.strip()[:16] or "wt-wt",
+            "safesearch": safesearch if safesearch in SAFESEARCH else "moderate",
+            "searxng_base_url": searxng_base_url.strip().rstrip("/"),
+            "firecrawl_base_url": firecrawl_base_url.strip().rstrip("/")
+            or "https://api.firecrawl.dev",
+            "firecrawl_api_key_encrypted": keep_or_replace(
+                firecrawl_api_key, current.get("firecrawl_api_key_encrypted") or ""
+            ),
+            "timeout": min(max(timeout, 5.0), 120.0),
+        },
+        key=settings_store.SEARCH,
+    )
+    log.info("web search %s by %s", "enabled" if enabled else "disabled", user.email)
+    return RedirectResponse("/admin/search?saved=1", status_code=status.HTTP_303_SEE_OTHER)
+
+
+@router.post("/test")
+async def test_search(request: Request, db: Db, user: AdminUser, query: str = Form("")):
+    """Run one real search and show what came back.
+
+    Against the stored settings rather than the unsaved form, so what is tested
+    is what a chat would actually do.
+    """
+    config = settings_store.search(db)
+    query = query.strip() or "lembas"
+
+    try:
+        results = await search_service.run(config, query)
+        message, kind = (
+            f"{search_service.provider(config.get('provider')).label} returned "
+            f"{len(results)} result{'' if len(results) == 1 else 's'}."
+        ), "success"
+    except SearchError as exc:
+        results, message, kind = [], exc.message, "error"
+
+    return render(
+        request,
+        "admin/_search_result.html",
+        {"results": results, "message": message, "message_kind": kind, "query": query},
+    )