Grounding pipeline and recipe-search settings API

recipes.Grounder ties search, fetch/extract, Rank, the photo cache and
normalize_recipe together. Ground(ctx, dishName, query) reuses a stored
source_url among the top candidates without fetching, otherwise tries the
ranked recipes best first and stores the photo, recipe, ingredients and
steps in one transaction, returning Grounded{recipe_id, photo_id, method,
minutes_total, difficulty, source_url, site_name} or a typed
*ErrUngroundable listing every reason. GroundURL grounds a pasted URL the
same way; GroundMany grounds items 3 at a time with per-item results.

PhotoCache is split into DownloadPhoto (fetch, decode, size check, no
writes) and CachePhoto(ctx, tx, photo), which records the row in the
caller's transaction; RemovePhotoFiles cleans up after a rollback.

Migration 0007 adds photo_id, method, difficulty and minutes_total to
recipes, and api_key_last4 to recipe_search_settings. SearXNG is now
called at recipe_search_settings.base_url.

GET/PATCH /api/v1/settings/recipe-search (Brave key sealed with
secretbox, only api_key_set and api_key_last4 returned) and POST
/api/v1/settings/recipe-search/test (searches "chicken tikka masala",
returns the count, 409 not_configured or 502 search_failed).

Maestro task 53afd59c-6c35-4af7-904c-6c167d1ad69d.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/server/settings_test.go

@@ -216,7 +216,7 @@ func TestHouseholdSettingsWithRealSession(t *testing.T) {
 	}
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
 	router, err := NewRouter(logger, "dev", nil, stubAuth{}, sessions, household.NewSettingsService(st),
-		newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
+		newTestSearch(t), newTestRunner(t), newTestPhotos(t), fstest.MapFS{"index.html": {Data: []byte(fixtureIndex)}})
 	if err != nil {
 		t.Fatal(err)
 	}