feat(03-03): build batch confirmation keyboard with inline buttons

- Replace placeholder 'Format Multiple Matches' with 'Build Batch Keyboard'
- Create inline_keyboard with 'Yes, <action> N containers' and 'Cancel' buttons
- Encode batch container IDs in callback_data (limit 4 for 64-byte constraint)
- Use HTTP Request for sendMessage (same pattern as suggestion flow)
- Format container list with bullet points in confirmation message

n8n-workflow.json

@@ -590,28 +590,27 @@
     },
     {
       "parameters": {
-        "jsCode": "// Multiple containers matched - placeholder for confirmation flow (Plan 03-02)\nconst data = $input.item.json;\nconst names = data.matches.map(m => m.Name).join(', ');\nreturn {\n  json: {\n    chatId: data.chatId,\n    text: `Found ${data.matchCount} containers matching '<b>${data.containerQuery}</b>': ${names}\\n\\nConfirmation required. (Coming in next update)`\n  }\n};"
+        "jsCode": "// Build batch confirmation keyboard for multiple matches\nconst matches = $json.matches;\nconst action = $json.action;\nconst chatId = $json.chatId;\nconst query = $json.containerQuery;\n\n// List matched container names\nconst names = matches.map(m => m.Name);\nconst shortIds = matches.map(m => m.Id.substring(0, 12));\n\n// Build callback_data - must be <=64 bytes\n// For batch: a=action code, c=array of short IDs, t=timestamp\nconst actionCode = action === 'start' ? 's' : action === 'stop' ? 't' : 'r';\nconst timestamp = Date.now();\n\n// Check size - if too many containers, callback_data might exceed 64 bytes\n// Each short ID is 12 chars, plus overhead. Max ~3-4 containers safely\nlet callbackData;\nlet limitedCount = shortIds.length;\nif (shortIds.length <= 4) {\n  callbackData = JSON.stringify({ a: actionCode, c: shortIds, t: timestamp });\n} else {\n  // Too many containers - limit to first 4\n  callbackData = JSON.stringify({ a: actionCode, c: shortIds.slice(0, 4), t: timestamp });\n  limitedCount = 4;\n}\n\n// Format container list\nconst listText = names.map(n => `  \\u2022 ${n}`).join('\\n');\n\n// Build action verb for button\nconst actionVerb = action.charAt(0).toUpperCase() + action.slice(1);\n\nreturn {\n  json: {\n    chat_id: chatId,\n    text: `Found <b>${matches.length}</b> containers matching '<b>${query}</b>':\\n\\n${listText}\\n\\n${actionVerb} all?`,\n    parse_mode: \"HTML\",\n    reply_markup: {\n      inline_keyboard: [\n        [\n          { text: `Yes, ${action} ${limitedCount} containers`, callback_data: callbackData },\n          { text: \"Cancel\", callback_data: '{\"a\":\"x\"}' }\n        ]\n      ]\n    },\n    // Store metadata for summary\n    _meta: {\n      action,\n      containers: matches,\n      timestamp,\n      limitedCount\n    }\n  }\n};"
       },
-      "id": "code-multiple-matches",
-      "name": "Format Multiple Matches",
+      "id": "code-build-batch-keyboard",
+      "name": "Build Batch Keyboard",
       "type": "n8n-nodes-base.code",
       "typeVersion": 2,
       "position": [1780, 500]
     },
     {
       "parameters": {
-        "resource": "message",
-        "operation": "sendMessage",
-        "chatId": "={{ $json.chatId }}",
-        "text": "={{ $json.text }}",
-        "additionalFields": {
-          "parse_mode": "HTML"
-        }
+        "method": "POST",
+        "url": "=https://api.telegram.org/bot{{ $credentials.telegramApi.accessToken }}/sendMessage",
+        "sendBody": true,
+        "specifyBody": "json",
+        "jsonBody": "={{ JSON.stringify({ chat_id: $json.chat_id, text: $json.text, parse_mode: $json.parse_mode, reply_markup: $json.reply_markup }) }}",
+        "options": {}
       },
-      "id": "telegram-send-multiple",
-      "name": "Send Multiple Matches",
-      "type": "n8n-nodes-base.telegram",
-      "typeVersion": 1.2,
+      "id": "http-send-batch-confirm",
+      "name": "Send Batch Confirmation",
+      "type": "n8n-nodes-base.httpRequest",
+      "typeVersion": 4.2,
       "position": [2000, 500],
       "credentials": {
         "telegramApi": {
@@ -1234,7 +1233,7 @@
         ],
         [
           {
-            "node": "Format Multiple Matches",
+            "node": "Build Batch Keyboard",
             "type": "main",
             "index": 0
           }
@@ -1315,11 +1314,11 @@
         ]
       ]
     },
-    "Format Multiple Matches": {
+    "Build Batch Keyboard": {
       "main": [
         [
           {
-            "node": "Send Multiple Matches",
+            "node": "Send Batch Confirmation",
             "type": "main",
             "index": 0
           }