feat: Add 15-minute chart filter to n8n workflow

- Extract timeframe from TradingView message format: 'SOLUSDT.P 15'
- Added 'timeframe-filter' IF node after Parse Signal
- Only allows trades on 15-minute chart signals
- Blocks 5-minute and other timeframe signals
- Regex pattern: \.P\s+(\d+) matches '.P 15' format

This prevents bot from trading on wrong timeframe alerts.

workflows/trading/n8n-complete-workflow.json

@@ -32,7 +32,7 @@
             },
             {
               "name": "timeframe",
-              "stringValue": "5"
+              "stringValue": "={{ $json.body.match(/\\.P\\s+(\\d+)/)?.[1] || '15' }}"
             }
           ]
         },
@@ -44,6 +44,24 @@
       "typeVersion": 3.2,
       "position": [440, 400]
     },
+    {
+      "parameters": {
+        "conditions": {
+          "string": [
+            {
+              "value1": "={{ $json.timeframe }}",
+              "operation": "equals",
+              "value2": "15"
+            }
+          ]
+        }
+      },
+      "id": "timeframe-filter",
+      "name": "15min Chart Only?",
+      "type": "n8n-nodes-base.if",
+      "typeVersion": 1,
+      "position": [540, 400]
+    },
     {
       "parameters": {
         "method": "POST",
@@ -72,7 +90,7 @@
       "name": "Check Risk",
       "type": "n8n-nodes-base.httpRequest",
       "typeVersion": 4,
-      "position": [640, 400]
+      "position": [740, 400]
     },
     {
       "parameters": {
@@ -89,7 +107,7 @@
       "name": "Risk Passed?",
       "type": "n8n-nodes-base.if",
       "typeVersion": 1,
-      "position": [840, 400]
+      "position": [940, 400]
     },
     {
       "parameters": {