Add photo backfill for failed dinners without a photo

Task 36c40130-a69a-46ed-a047-2cdc5ee2d2e0 (Feature 23, task 1 of 2).

A backfill_dinner_photos job grounds, by name with the existing
recipes.Grounder.Ground, every unarchived dinner whose grounding failed
and that has no photo and no pasted recipe_url. Ground already tries the
ranked candidates best first and keeps the first whose photo caches and
whose ingredients normalize, reusing stored recipes and photos. Success
records the recipe and photo as grounded; a failure leaves the dinner
failed with the new grounding_error for the fix-recipe flow, without
stopping its siblings. Writes are guarded on status, photo and
grounding_revision, so grounded, manual, pending, renamed and archived
dinners are never touched.

POST /api/v1/settings/photo-backfill starts a full pass and answers 202
with the job id; the kind is service-only.

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

internal/db/querier.go

@@ -175,6 +175,13 @@ type Querier interface {
 	// unknown id, returns sql.ErrNoRows. A method, minutes_total or difficulty
 	// no longer as observed is kept: a member edited it while it was grounding.
 	GroundDinner(ctx context.Context, arg GroundDinnerParams) (Dinner, error)
+	// Records a photo backfill's grounding of a dinner it listed, while the
+	// dinner is still unarchived, failed, photoless, without a recipe_url and at
+	// the grounding_revision it was listed at; a dinner grounded by hand,
+	// renamed or archived meanwhile is left as it is (0 rows). Like
+	// GroundPendingDinner it keeps a method, minutes_total or difficulty a
+	// member already set.
+	GroundFailedDinner(ctx context.Context, arg GroundFailedDinnerParams) (int64, error)
 	// Records the background grounding of an unarchived dinner still pending at
 	// the grounding_revision it was grounded for; a dinner grounded some other
 	// way, renamed or archived meanwhile is left as it is (0 rows). A method,
@@ -206,6 +213,12 @@ type Querier interface {
 	// The pending Rotation checks whose dinner is still tried, oldest plan
 	// date first, with their dinners.
 	ListPendingRotationReviews(ctx context.Context) ([]ListPendingRotationReviewsRow, error)
+	// The dinners a photo backfill grounds by name: unarchived, failed, with no
+	// photo and no pasted recipe_url (the household's own link is never
+	// replaced by a search), ordered by normalized name. A non-NULL id narrows
+	// the list to that dinner. Grounded, manual and pending dinners are never
+	// listed: they have a recipe, or a ground_dinner job grounding them.
+	ListPhotoBackfillDinners(ctx context.Context, id sql.NullString) ([]Dinner, error)
 	// The days of plan plan_id with their dinners, Monday first. A day with
 	// no dinner is left out.
 	ListPlanDays(ctx context.Context, planID string) ([]ListPlanDaysRow, error)
@@ -307,6 +320,9 @@ type Querier interface {
 	// Records a new draft over plan id: its status and note, raising its
 	// revision.
 	RedraftWeekPlan(ctx context.Context, arg RedraftWeekPlanParams) error
+	// Records why a photo backfill could not ground a dinner it listed, under
+	// the same conditions as GroundFailedDinner (0 rows otherwise).
+	RefailDinnerGrounding(ctx context.Context, arg RefailDinnerGroundingParams) (int64, error)
 	// Records a generation of list id from plan plan_id.
 	RegenerateShoppingList(ctx context.Context, arg RegenerateShoppingListParams) error
 	// Records a failed delivery and when to try again. The lease must still be