feat: add remote worker system for distributed translation

- Add remote translator worker (Docker) that connects via WebSocket
- Add backend Go handlers for remote worker CRUD (REST + WebSocket)
- Add frontend Admin panel for managing remote workers
- Add ProtectedRoute component to secure admin routes
- Add PostgreSQL schema for remote_workers table
- Fix duplicate Load function in config.go
- Fix frontend duplicate fetchStatus function
- Fix Dockerfiles missing go.sum (use go mod download + tidy)

Features:
- Workers connect to server via WebSocket (no ports needed)
- API key authentication per worker
- Job assigner automatically distributes translation jobs
- Worker status tracking (online/offline/disabled)
- Timeout handling for stuck jobs

backend/internal/models/remote_worker.go

@@ -0,0 +1,41 @@
+package models
+
+import "time"
+
+type RemoteWorker struct {
+	ID           int       `json:"id"`
+	Name         string    `json:"name"`
+	APIKey       string    `json:"api_key,omitempty"`
+	Capabilities string    `json:"capabilities"`
+	Status       string    `json:"status"`
+	LastSeen     *time.Time `json:"last_seen,omitempty"`
+	CreatedAt    time.Time `json:"created_at"`
+}
+
+type TranslationJob struct {
+	ID        int64  `json:"id"`
+	NewsID    int64  `json:"noticia_id"`
+	LangFrom  string `json:"lang_from"`
+	LangTo    string `json:"lang_to"`
+	Title     string `json:"title"`
+	Summary   string `json:"summary"`
+}
+
+type TranslationResult struct {
+	JobID      int64  `json:"job_id"`
+	TitleTr   string `json:"title_trad"`
+	SummaryTr string `json:"resumen_trad"`
+	Error     string `json:"error,omitempty"`
+}
+
+type WSClientMessage struct {
+	Type         string              `json:"type"`
+	Capabilities string              `json:"capabilities,omitempty"`
+	WorkerName  string              `json:"worker_name,omitempty"`
+	Result      *TranslationResult  `json:"result,omitempty"`
+}
+
+type WSServerMessage struct {
+	Type string          `json:"type"`
+	Job  *TranslationJob `json:"job,omitempty"`
+}