Fix Map.Scan nil panic and Date zero-value rejection on MySQL strict mode

- Map.Scan: auto-initialize shards when loading into a zero-value Map (e.g. via GORM); prevents nil pointer panic on MSet
- Date.GormValue: return NULL for zero dates on all databases, not just PostgreSQL; MySQL 5.7+ STRICT_TRANS_TABLES rejects '0000-00-00'

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

Author: getevo

lib/db/types/date.go

@@ -77,15 +77,11 @@ func (t Date) Value() (driver.Value, error) {
 }
 
 // GormValue implements GormValuerInterface for dialect-aware date handling.
-// PostgreSQL rejects "0000-00-00" as an invalid date, so we return NULL instead.
+// Zero dates (year < 1000) are stored as NULL to avoid invalid date errors in
+// strict-mode databases (PostgreSQL, MySQL 5.7+ with STRICT_TRANS_TABLES).
 func (t Date) GormValue(ctx context.Context, db *gorm.DB) clause.Expr {
 	if t.Year() < 1000 {
-		switch db.Dialector.Name() {
-		case "postgres":
-			return gorm.Expr("NULL")
-		default:
-			return gorm.Expr("?", "0000-00-00")
-		}
+		return gorm.Expr("NULL")
 	}
 	return gorm.Expr("?", fmt.Sprintf("%d-%02d-%02d", t.Year(), t.Month(), t.Day()))
 }

lib/db/types/map.go

@@ -219,6 +219,22 @@ func (m *Map[K, V]) Scan(src any) error {
 	if err := json.Unmarshal(bytes, &all); err != nil {
 		return err
 	}
+	// Initialize shards if the map was created as a zero value (e.g. loaded by GORM).
+	if m.shards == nil {
+		m.shards = make([]*ConcurrentMapShared[K, V], SHARD_COUNT)
+		for i := range m.shards {
+			m.shards[i] = &ConcurrentMapShared[K, V]{items: make(map[K]V)}
+		}
+		// Default sharding: fmt.Sprintf hash (safe for any comparable K).
+		m.sharding = func(key K) uint32 {
+			h := uint32(2166136261)
+			for _, c := range fmt.Sprintf("%v", key) {
+				h ^= uint32(c)
+				h *= 16777619
+			}
+			return h
+		}
+	}
 	m.MSet(all)
 	return nil
 }