feat(graph): add GraphNode, GraphEdge, GraphGroup, GraphView domain entities

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/modules/graph/domain/entities.py

@@ -0,0 +1,31 @@
+from dataclasses import dataclass
+
+
+@dataclass
+class GraphNode:
+    id: str
+    type: str           # capability, module, entity, integration, ...
+    label: str
+    status: str         # FileStatus or "unknown"
+    group_id: str
+
+
+@dataclass
+class GraphEdge:
+    source: str
+    target: str
+    relation: str       # traces_to, depends_on, owns, integrates_with, ...
+
+
+@dataclass
+class GraphGroup:
+    id: str
+    label: str
+    layer: str          # business, application, data, technology, cross-layer
+
+
+@dataclass
+class GraphView:
+    nodes: list[GraphNode]
+    edges: list[GraphEdge]
+    groups: list[GraphGroup]