Offer Search again only where the photo backfill runs (Maestro 7a468d2d, review F1/F2)

F1: every dinner response now carries photo_backfill_eligible, computed
by the exported dinners.PhotoBackfillEligible: the condition
ListPhotoBackfillDinners lists by and GroundFailedDinner and
RefailDinnerGrounding write under (unarchived, failed, no photo, no
pasted recipe_url). A test holds the flag to ListPhotoBackfillDinners
for an eligible dinner and for grounded, linked and archived ones. The
fix-recipe sheet shows "Search again" only when the flag is set, so a
dinner with a pasted link is never offered it, whatever its reason.

F2: a dinner absent from the backfill result now reads "This dinner was
not included in that search." instead of claiming a pasted link.

Task: 7a468d2d-4a9b-45f2-b626-a7bed5f671df

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

internal/dinners/dinners.go

@@ -79,6 +79,11 @@ type Dinner struct {
 	UpdatedBy      *string `json:"updated_by"`
 	CreatedAt      string  `json:"created_at"`
 	UpdatedAt      string  `json:"updated_at"`
+
+	// PhotoBackfillEligible is whether a photo backfill grounds the dinner
+	// (PhotoBackfillEligible): false for one with a pasted recipe link,
+	// which a search never replaces.
+	PhotoBackfillEligible bool `json:"photo_backfill_eligible"`
 }
 
 // NewRegular is a Regular to add: its Name, which the household always
@@ -712,6 +717,8 @@ func fromRow(r db.Dinner) Dinner {
 		UpdatedBy:       nullString(r.UpdatedBy),
 		CreatedAt:       r.CreatedAt,
 		UpdatedAt:       r.UpdatedAt,
+
+		PhotoBackfillEligible: PhotoBackfillEligible(r),
 	}
 	if r.MinutesTotal.Valid {
 		d.MinutesTotal = &r.MinutesTotal.Int64