macOS Time Machine AFP monitoring: backup_time update on file modification

- Added afp_monitor.rs module to track AFP_AfpInfo backup_time
- Open struct now has 'modified' flag to track file modifications
- write.rs sets modified=true on successful write
- close.rs calls AfpMonitor::update_backup_time() on modified files
- create.rs calls AfpMonitor::init_afp_info() on new file creation
- AFP_AfpInfo stored as xattr com.apple.aapl.AfpInfo
- backup_time updated to current epoch time on modification

Also includes:
- LZ4 compression using lz4_flex crate
- Case sensitivity conditional on backend capabilities
- LDAP cfg feature gate fix
- RAID rebuild reconstruction implementation
- DOS attributes xattr persistence
- Snapshot disk persistence

Tests: 201 smb-server, 452 markbase-core (653 total)

vendor/smb-server/src/conn/state.rs

@@ -233,6 +233,8 @@ pub struct Session {
     pub signing_required: bool,
     /// Whether encryption is enabled for this session
     pub encryption_enabled: bool,
+    /// Negotiated cipher algorithm for this session
+    pub encryption_cipher: Option<CipherAlgorithm>,
     pub trees: RwLock<HashMap<u32, Arc<RwLock<TreeConnect>>>>,
     /// 3.1.1: snapshot taken at SESSION_SETUP completion (after the request
     /// hash but before the response is hashed). Used as KDF context.
@@ -250,6 +252,7 @@ impl Session {
         encryption_key: Option<[u8; 16]>,
         signing_required: bool,
         encryption_enabled: bool,
+        encryption_cipher: Option<CipherAlgorithm>,
         preauth_snapshot: Option<[u8; 64]>,
     ) -> Self {
         Self {
@@ -260,6 +263,7 @@ impl Session {
             encryption_key,
             signing_required,
             encryption_enabled,
+            encryption_cipher,
             trees: RwLock::new(HashMap::new()),
             preauth_snapshot,
             next_tree_id: AtomicU32::new(1),
@@ -323,6 +327,8 @@ pub struct Open {
     pub lease_key: Option<[u8; 16]>,  // LeaseKey GUID
     pub lease_state: Option<u32>,     // LeaseState (READ/HANDLE/WRITE)
     pub lease_flags: Option<u32>,     // LeaseFlags (BREAKING etc.)
+    // AFP monitoring (Time Machine)
+    pub modified: bool,               // Track if file was modified
 }
 
 impl Open {
@@ -349,6 +355,7 @@ impl Open {
             lease_key: None,
             lease_state: None,
             lease_flags: None,
+            modified: false,
         }
     }
 }