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/handlers/remote_worker.go

@@ -0,0 +1,187 @@
+package handlers
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"log"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/rss2/backend/internal/db"
+	"github.com/rss2/backend/internal/models"
+)
+
+func CreateRemoteWorker(c *gin.Context) {
+	var req struct {
+		Name         string `json:"name" binding:"required"`
+		Capabilities string `json:"capabilities"`
+	}
+
+	if err := c.ShouldBindJSON(&req); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "Invalid request", "message": err.Error()})
+		return
+	}
+
+	if req.Capabilities == "" {
+		req.Capabilities = "cpu"
+	}
+
+	apiKey := generateAPIKey()
+
+	ctx := c.Request.Context()
+	var workerID int
+	err := db.GetPool().QueryRow(ctx, `
+		INSERT INTO remote_workers (name, api_key, capabilities, status, created_at)
+		VALUES ($1, $2, $3, 'offline', NOW())
+		RETURNING id
+	`, req.Name, apiKey, req.Capabilities).Scan(&workerID)
+
+	if err != nil {
+		log.Printf("Error creating remote worker: %v", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to create worker"})
+		return
+	}
+
+	c.JSON(http.StatusCreated, gin.H{
+		"id":           workerID,
+		"name":         req.Name,
+		"api_key":      apiKey,
+		"capabilities": req.Capabilities,
+		"status":       "offline",
+	})
+}
+
+func ListRemoteWorkers(c *gin.Context) {
+	ctx := c.Request.Context()
+
+	rows, err := db.GetPool().Query(ctx, `
+		SELECT id, name, api_key, capabilities, status, last_seen, created_at
+		FROM remote_workers
+		ORDER BY created_at DESC
+	`)
+	if err != nil {
+		log.Printf("Error listing remote workers: %v", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to list workers"})
+		return
+	}
+	defer rows.Close()
+
+	var workers []models.RemoteWorker
+	for rows.Next() {
+		var w models.RemoteWorker
+		if err := rows.Scan(&w.ID, &w.Name, &w.APIKey, &w.Capabilities, &w.Status, &w.LastSeen, &w.CreatedAt); err != nil {
+			log.Printf("Error scanning worker: %v", err)
+			continue
+		}
+		workers = append(workers, w)
+	}
+
+	if workers == nil {
+		workers = []models.RemoteWorker{}
+	}
+
+	c.JSON(http.StatusOK, workers)
+}
+
+func GetRemoteWorker(c *gin.Context) {
+	id := c.Param("id")
+	ctx := c.Request.Context()
+
+	var w models.RemoteWorker
+	err := db.GetPool().QueryRow(ctx, `
+		SELECT id, name, api_key, capabilities, status, last_seen, created_at
+		FROM remote_workers
+		WHERE id = $1
+	`, id).Scan(&w.ID, &w.Name, &w.APIKey, &w.Capabilities, &w.Status, &w.LastSeen, &w.CreatedAt)
+
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Worker not found"})
+		return
+	}
+
+	var stats struct {
+		JobsCompleted int `json:"jobs_completed"`
+		JobsPending   int `json:"jobs_pending"`
+	}
+
+	db.GetPool().QueryRow(ctx, `
+		SELECT COUNT(*) FROM traducciones WHERE worker_id = $1 AND status = 'done'
+	`, id).Scan(&stats.JobsCompleted)
+
+	db.GetPool().QueryRow(ctx, `
+		SELECT COUNT(*) FROM traducciones WHERE worker_id = $1 AND status = 'pending'
+	`, id).Scan(&stats.JobsPending)
+
+	c.JSON(http.StatusOK, gin.H{
+		"worker": w,
+		"stats":  stats,
+	})
+}
+
+func DeleteRemoteWorker(c *gin.Context) {
+	id := c.Param("id")
+	ctx := c.Request.Context()
+
+	result, err := db.GetPool().Exec(ctx, `
+		DELETE FROM remote_workers WHERE id = $1
+	`, id)
+
+	if err != nil {
+		log.Printf("Error deleting remote worker: %v", err)
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to delete worker"})
+		return
+	}
+
+	if result.RowsAffected() == 0 {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Worker not found"})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"message": "Worker deleted"})
+}
+
+func ToggleRemoteWorker(c *gin.Context) {
+	id := c.Param("id")
+	ctx := c.Request.Context()
+
+	var currentStatus string
+	err := db.GetPool().QueryRow(ctx, `SELECT status FROM remote_workers WHERE id = $1`, id).Scan(&currentStatus)
+	if err != nil {
+		c.JSON(http.StatusNotFound, gin.H{"error": "Worker not found"})
+		return
+	}
+
+	newStatus := "disabled"
+	if currentStatus == "disabled" {
+		newStatus = "offline"
+	}
+
+	_, err = db.GetPool().Exec(ctx, `UPDATE remote_workers SET status = $1 WHERE id = $2`, newStatus, id)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to update worker status"})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"status": newStatus})
+}
+
+func RegenerateAPIKey(c *gin.Context) {
+	id := c.Param("id")
+	ctx := c.Request.Context()
+
+	newAPIKey := generateAPIKey()
+
+	_, err := db.GetPool().Exec(ctx, `UPDATE remote_workers SET api_key = $1 WHERE id = $2`, newAPIKey, id)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"error": "Failed to regenerate API key"})
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{"api_key": newAPIKey})
+}
+
+func generateAPIKey() string {
+	bytes := make([]byte, 32)
+	rand.Read(bytes)
+	return hex.EncodeToString(bytes)
+}