feat(proxmox): add journalctl streaming API endpoint for LXC containers

Add new /api/v1/proxmox/journalctl/:node/:vmid/:service endpoint that
streams real-time journalctl output from Proxmox LXC containers via
WebSocket connection. This enables live monitoring of container services
from the GoDoxy WebUI.

Implementation includes:
- New proxmox API handler with path parameter validation
- WebSocket upgrade for streaming output
- LXCCommand helper for executing commands over Proxmox VNC websocket
- LXCJournalctl wrapper for convenient journalctl -u service -f invocation
- Updated API documentation with proxmox integration

internal/api/v1/docs/swagger.yaml

@@ -2076,6 +2076,48 @@ paths:
       tags:
       - agent
       x-id: verify
+  /api/v1/proxmox/journalctl/{node}/{vmid}/{service}:
+    get:
+      consumes:
+      - application/json
+      description: Get journalctl output
+      parameters:
+      - in: path
+        name: node
+        required: true
+        type: string
+      - in: path
+        name: service
+        required: true
+        type: string
+      - in: path
+        name: vmid
+        required: true
+        type: integer
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: Journalctl output
+          schema:
+            type: string
+        "400":
+          description: Invalid request
+          schema:
+            $ref: '#/definitions/ErrorResponse'
+        "403":
+          description: Unauthorized
+          schema:
+            $ref: '#/definitions/ErrorResponse'
+        "500":
+          description: Internal server error
+          schema:
+            $ref: '#/definitions/ErrorResponse'
+      summary: Get journalctl output
+      tags:
+      - proxmox
+      - websocket
+      x-id: journalctl
   /auth/callback:
     post:
       description: Handles the callback from the provider after successful authentication