feat(provider): add google project and location fields

Add support for Google Cloud-specific configuration in provider models.
New fields `GoogleProject` and `GoogleLocation` are now included in the
Provider DTO, database model, API handlers, and sync service snapshots.

- Extend Provider struct in model with gorm/json tags
- Update ProviderDTO with omitempty JSON tags
- Include fields in handler create/update logic with trim
- Add fields to providerSnapshot for sync operations

internal/dto/provider.go

@@ -4,16 +4,18 @@ import "time"
 
 // ProviderDTO defines inbound payload for provider creation/update.
 type ProviderDTO struct {
-	Name      string    `json:"name"`
-	Type      string    `json:"type"`
-	BaseURL   string    `json:"base_url"`
-	APIKey    string    `json:"api_key"`
-	Group     string    `json:"group"`
-	Models    []string  `json:"models"` // List of supported model names
-	Status    string    `json:"status"`
-	AutoBan   *bool     `json:"auto_ban,omitempty"`
-	BanReason string    `json:"ban_reason,omitempty"`
-	BanUntil  time.Time `json:"ban_until,omitempty"`
+	Name           string    `json:"name"`
+	Type           string    `json:"type"`
+	BaseURL        string    `json:"base_url"`
+	APIKey         string    `json:"api_key"`
+	GoogleProject  string    `json:"google_project,omitempty"`
+	GoogleLocation string    `json:"google_location,omitempty"`
+	Group          string    `json:"group"`
+	Models         []string  `json:"models"` // List of supported model names
+	Status         string    `json:"status"`
+	AutoBan        *bool     `json:"auto_ban,omitempty"`
+	BanReason      string    `json:"ban_reason,omitempty"`
+	BanUntil       time.Time `json:"ban_until,omitempty"`
 
 	// Optional control params
 	SkipRouting bool `json:"skip_routing,omitempty"` // if true, do not add to routing tables (e.g., disabled)