✨ feat(sync): multi-language sync wizard, backend locale support, and conflict modal UX improvements

Frontend (web)
- ModelsActions.jsx
  - Replace “Sync Official” with “Sync” and open a new two-step SyncWizard.
  - Pass selected locale through to preview, sync, and overwrite flows.
  - Keep conflict resolution flow; inject locale into overwrite submission.

- New: models/modals/SyncWizardModal.jsx
  - Two-step wizard: (1) method selection (config-sync disabled for now), (2) language selection (en/zh/ja).
  - Horizontal, centered Radio cards; returns { option, locale } via onConfirm.

- UpstreamConflictModal.jsx
  - Add search input (model fuzzy search) and native pagination.
  - Column header checkbox now only applies to rows in the current filtered result.
  - Fix “Cannot access ‘filteredDataSource’ before initialization”.
  - Refactor with useMemo/useCallback; extract helpers to remove duplicated logic:
    - getPresentRowsForField, getHeaderState, applyHeaderChange
  - Minor code cleanups and stability improvements.

- i18n (en.json)
  - Add strings for the sync wizard and related actions (Sync, Sync Wizard, Select method/source/language, etc.).
  - Adjust minor translations.

Hooks
- useModelsData.jsx
  - Extend previewUpstreamDiff, syncUpstream, applyUpstreamOverwrite to accept options with locale.
  - Send locale via query/body accordingly.

Backend (Go)
- controller/model_sync.go
  - Accept locale from query/body and resolve i18n upstream URLs.
  - Add SYNC_UPSTREAM_BASE for upstream base override (default: https://basellm.github.io/llm-metadata).
  - Make HTTP timeouts/retries/limits configurable:
    - SYNC_HTTP_TIMEOUT_SECONDS, SYNC_HTTP_RETRY, SYNC_HTTP_MAX_MB
  - Add ETag-based caching and support both envelope and pure array JSON formats.
  - Concurrently fetch vendors and models; improve error responses with locale and source URLs.
  - Include source meta (locale, models_url, vendors_url) in success payloads.

Notes
- No breaking changes expected.
- Lint passes for touched files.

model/model_meta.go

@@ -20,18 +20,18 @@ type BoundChannel struct {
 }
 
 type Model struct {
-	Id          int            `json:"id"`
-	ModelName   string         `json:"model_name" gorm:"size:128;not null;uniqueIndex:uk_model_name_delete_at,priority:1"`
-	Description string         `json:"description,omitempty" gorm:"type:text"`
-	Icon        string         `json:"icon,omitempty" gorm:"type:varchar(128)"`
-	Tags        string         `json:"tags,omitempty" gorm:"type:varchar(255)"`
-	VendorID    int            `json:"vendor_id,omitempty" gorm:"index"`
-	Endpoints   string         `json:"endpoints,omitempty" gorm:"type:text"`
-	Status      int            `json:"status" gorm:"default:1"`
-	SyncOfficial int           `json:"sync_official" gorm:"default:1"`
-	CreatedTime int64          `json:"created_time" gorm:"bigint"`
-	UpdatedTime int64          `json:"updated_time" gorm:"bigint"`
-	DeletedAt   gorm.DeletedAt `json:"-" gorm:"index;uniqueIndex:uk_model_name_delete_at,priority:2"`
+	Id           int            `json:"id"`
+	ModelName    string         `json:"model_name" gorm:"size:128;not null;uniqueIndex:uk_model_name_delete_at,priority:1"`
+	Description  string         `json:"description,omitempty" gorm:"type:text"`
+	Icon         string         `json:"icon,omitempty" gorm:"type:varchar(128)"`
+	Tags         string         `json:"tags,omitempty" gorm:"type:varchar(255)"`
+	VendorID     int            `json:"vendor_id,omitempty" gorm:"index"`
+	Endpoints    string         `json:"endpoints,omitempty" gorm:"type:text"`
+	Status       int            `json:"status" gorm:"default:1"`
+	SyncOfficial int            `json:"sync_official" gorm:"default:1"`
+	CreatedTime  int64          `json:"created_time" gorm:"bigint"`
+	UpdatedTime  int64          `json:"updated_time" gorm:"bigint"`
+	DeletedAt    gorm.DeletedAt `json:"-" gorm:"index;uniqueIndex:uk_model_name_delete_at,priority:2"`
 
 	BoundChannels []BoundChannel `json:"bound_channels,omitempty" gorm:"-"`
 	EnableGroups  []string       `json:"enable_groups,omitempty" gorm:"-"`