feat(proxmox): add LXC container stats endpoint with streaming support

Implement a new API endpoint to retrieve real-time statistics for Proxmox
LXC containers, similar to `docker stats` functionality.

Changes:
- Add `GET /api/v1/proxmox/stats/:node/:vmid` endpoint with HTTP and WebSocket support
- Implement resource polling loop to cache VM metadata every 3 seconds
- Create `LXCStats()` method with streaming (websocket) and single-shot modes
- Format output as: STATUS|CPU%|MEM USAGE/LIMIT|MEM%|NET I/O|BLOCK I/O
- Add `GetResource()` method for efficient VM resource lookup by kind and ID
- Fix task creation bug using correct client reference

Example response:
  running|31.1%|9.6GiB/20GiB|48.87%|4.7GiB/3.3GiB|25GiB/36GiB

internal/api/v1/docs/swagger.json

@@ -218,6 +218,12 @@
               "$ref": "#/definitions/ErrorResponse"
             }
           },
+          "404": {
+            "description": "Node not found",
+            "schema": {
+              "$ref": "#/definitions/ErrorResponse"
+            }
+          },
           "500": {
             "description": "Internal server error",
             "schema": {
@@ -229,6 +235,70 @@
         "operationId": "journalctl"
       }
     },
+    "/api/v1/proxmox/stats/{node}/{vmid}": {
+      "get": {
+        "description": "Get proxmox stats in format of \"STATUS|CPU%%|MEM USAGE/LIMIT|MEM%%|NET I/O|BLOCK I/O\"",
+        "consumes": [
+          "application/json"
+        ],
+        "produces": [
+          "application/json"
+        ],
+        "tags": [
+          "proxmox",
+          "websocket"
+        ],
+        "summary": "Get proxmox stats",
+        "parameters": [
+          {
+            "type": "string",
+            "name": "node",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "integer",
+            "name": "vmid",
+            "in": "path",
+            "required": true
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Stats output",
+            "schema": {
+              "type": "string"
+            }
+          },
+          "400": {
+            "description": "Invalid request",
+            "schema": {
+              "$ref": "#/definitions/ErrorResponse"
+            }
+          },
+          "403": {
+            "description": "Unauthorized",
+            "schema": {
+              "$ref": "#/definitions/ErrorResponse"
+            }
+          },
+          "404": {
+            "description": "Node not found",
+            "schema": {
+              "$ref": "#/definitions/ErrorResponse"
+            }
+          },
+          "500": {
+            "description": "Internal server error",
+            "schema": {
+              "$ref": "#/definitions/ErrorResponse"
+            }
+          }
+        },
+        "x-id": "stats",
+        "operationId": "stats"
+      }
+    },
     "/auth/callback": {
       "post": {
         "description": "Handles the callback from the provider after successful authentication",