feat: advance local-first workspace checklist

- add admin access-policy UI and local access control surfaces

- add local markdown conflict resolution UI and smoke coverage

- add ACP local agent changed-files audit scaffold and read-only write guard

- document current P0-P2 checklist progress and verification evidence

rust/crates/mnote-web/src/page_aggregate/builder.rs

@@ -344,6 +344,7 @@ impl PageAggregateBuilder {
                 content: self.content,
                 revision: self.revision,
                 conflict_detection_key: self.conflict_detection_key,
+                file_version: Value::Null,
                 block_document: block_document.unwrap_or(Value::Null),
                 block_projection_version,
                 projection_source: "builder.content".into(),