Add named project snapshots

docs/circuit-list-editor-api.md

@@ -32,6 +32,18 @@ this value for optimistic concurrency checks.
   - body: `{ "expectedRevision": 1 }`
   - executes the eligible inverse or forward command as a new auditable
     revision
+- `GET /projects/:projectId/snapshots`
+  - lists named logical snapshot metadata without returning payload JSON
+- `POST /projects/:projectId/snapshots`
+  - body:
+    `{ "expectedRevision": 12, "name": "Vor Ausschreibung", "description": "Optional" }`
+  - atomically captures the complete project-scoped runtime state at the
+    expected revision
+  - returns `201` with source revision, schema version, SHA-256 and creation
+    metadata
+  - snapshot creation does not increment the project revision or alter
+    undo/redo stacks
+  - duplicate names and stale revisions return `409`
 
 The public dispatcher currently supports `circuit.update`, `circuit.insert`,
 `circuit.delete`, `circuit-device-row.update`,