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/domain/fruit.go

@@ -2,6 +2,14 @@ package domain
 
 import "time"
 
+// FruitTypeAliases maps combined-type alias labels to the enum values they expand to.
+var FruitTypeAliases = map[string][]string{
+	"Birnen- und Quittensorten":  {"Birnensorten", "Quittensorten"},
+	"Aprikosen und Pfirsiche":    {"Aprikosen", "Pfirsiche"},
+	"Mirabellen und Reineclauden": {"Mirabellen", "Renekloden"},
+	"Pflaumen und Zwetschen":     {"Pflaumen", "Zwetschen"},
+}
+
 type Fruit struct {
 	ID          int          `json:"id"`
 	Name        string       `json:"name"`