feat: fruit search by name/synonym and type filter (story #06)

Backend: List repo query gains name (ILIKE with wildcard escaping on
name + synonym LEFT JOIN, SELECT DISTINCT) and types (ANY cast) params;
handler parses ?name= and ?type=, resolves combined-type aliases from
domain.FruitTypeAliases, validates plain types against validFruitTypes
to prevent Postgres enum cast errors. ORDER BY f.name, f.id for stable
pagination.

Frontend: listFruits gains optional {name, type} params; fruitStore adds
searchName/searchType state and setSearch action (resets offset, refetches);
FruitList.vue wires text input (debounced 300 ms + Enter) and flat type
dropdown (17 enum values + 4 aliases per spec §5 order); debounce timer
cleared on unmount.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/repository/fruit_repo_integration_test.go

@@ -97,7 +97,7 @@ func TestFruitRepoIntegration(t *testing.T) {
 	}
 
 	// List
-	fruits, total, err := repo.List(ctx, 50, 0)
+	fruits, total, err := repo.List(ctx, 50, 0, "", nil)
 	if err != nil {
 		t.Fatalf("List: %v", err)
 	}