Expose protected tree structure

docs/circuit-list-editor-api.md

@@ -230,7 +230,11 @@ returns HTTP `409` with `PROJECT_HISTORY_OPERATION_UNAVAILABLE`.
 ### Tree Endpoint
 
 - `GET /projects/:projectId/circuit-lists/:circuitListId/tree`
-- Purpose: returns section/circuit/device-row tree with calculated row and circuit totals.
+- Purpose: returns fixed header components, grouped sections with optional
+  protection components, complete circuit/device-row blocks and auxiliary
+  footer components. Circuit and component protection devices use their
+  separate one-to-one DTOs. Calculated row, circuit, section and board totals
+  remain included.
 
 Response sketch:
 
@@ -238,16 +242,47 @@ Response sketch:
 {
   "circuitListId": "cl_1",
   "currentRevision": 12,
+  "headerComponents": [
+    {
+      "id": "cmp_main",
+      "equipmentIdentifier": "-Q0",
+      "name": "Hauptschalter",
+      "role": "main_switch",
+      "placement": "header"
+    }
+  ],
   "sections": [
     {
       "id": "sec_1",
       "key": "lighting",
-      "prefix": "-1F",
+      "prefix": "-1F1.",
+      "category": "lighting",
+      "groupNumber": 1,
+      "components": [
+        {
+          "id": "cmp_rcd",
+          "equipmentIdentifier": "-1Q1.0",
+          "name": "Gruppen-FI",
+          "role": "group_residual_current_protection",
+          "placement": "group",
+          "protectionDevice": {
+            "type": "FI",
+            "ratedCurrentA": 40,
+            "rcdType": "A",
+            "ratedResidualCurrentMa": 30
+          }
+        }
+      ],
       "circuits": [
         {
           "id": "cir_1",
-          "equipmentIdentifier": "-1F1",
+          "equipmentIdentifier": "-1F1.1",
           "circuitTotalPower": 4.2,
+          "protectionDevice": {
+            "type": "LS",
+            "ratedCurrentA": 10,
+            "tripCharacteristic": "B"
+          },
           "deviceRows": [
             {
               "id": "row_1",
@@ -258,6 +293,15 @@ Response sketch:
         }
       ]
     }
+  ],
+  "footerComponents": [
+    {
+      "id": "cmp_actor",
+      "equipmentIdentifier": "-K1",
+      "name": "KNX Schaltaktor",
+      "role": "auxiliary",
+      "placement": "footer"
+    }
   ]
 }
 ```