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/recipes/rank.go

@@ -45,12 +45,13 @@ type Ranked struct {
 }
 
 // Rank fetches and extracts the first RankDepth candidates concurrently and
-// returns those whose recipe has ingredients and an image, highest Score
-// first; equal scores keep search order.
+// returns those whose recipe is usable — it has ingredients and an image,
+// and any total time it gives is positive — highest Score first; equal
+// scores keep search order.
 //
 // Every candidate that is not ranked — its fetch failed, its page holds no
-// valid recipe, or the recipe lacks ingredients or an image — is reported,
-// never dropped silently: when some are ranked the error is
+// valid recipe, or the recipe is not usable — is reported, never dropped
+// silently: when some are ranked the error is
 // ErrCandidatesUnranked, returned together with the ranked ones; when none
 // are it is ErrNoUsableRecipe with no results. Either is joined with each
 // unranked candidate's URL and reason. A cancelled ctx returns only its
@@ -108,15 +109,26 @@ func rankOne(ctx context.Context, f PageFetcher, dish string, c Candidate) (Rank
 	if err != nil {
 		return Ranked{}, err
 	}
-	if len(r.Ingredients) == 0 {
-		return Ranked{}, ErrNoIngredients
-	}
-	if r.ImageURL == "" {
-		return Ranked{}, ErrNoImage
+	if err := usable(r); err != nil {
+		return Ranked{}, err
 	}
 	return Ranked{Candidate: c, Recipe: r, Score: harness.Similarity(r.Title, dish) + completeness(r)}, nil
 }
 
+// usable says why r cannot ground a dish: it has no ingredients or no
+// image, or a total time that is not positive.
+func usable(r Recipe) error {
+	switch {
+	case len(r.Ingredients) == 0:
+		return ErrNoIngredients
+	case r.ImageURL == "":
+		return ErrNoImage
+	case r.TotalMinutes != nil && *r.TotalMinutes <= 0:
+		return ErrTotalTimeNotPositive
+	}
+	return nil
+}
+
 // completeness is a quarter for each of ingredients, image, steps and total
 // minutes the recipe has.
 func completeness(r Recipe) float64 {