Implement SMB Oplocks Phase 1-2

Phase 1: Data structures
- Add oplock_level and share_access fields to Open struct
- Update Open::new() signature with new parameters
- Update handlers/create.rs to pass oplock params

Phase 2: OplockManager
- Create oplock.rs with OplockManager struct
- OplockEntry for tracking per-client oplock state
- can_grant() - check ShareAccess compatibility
- register() / unregister() - lifecycle management
- break_oplock() - generate OPLOCK_BREAK_NOTIFICATION
- Add OplockManager to ServerState
- Add Hash trait to SmbPath for HashMap key

All 229 tests pass.

vendor/smb-server/src/server.rs

@@ -196,6 +196,8 @@ pub struct ServerState {
     /// iteration and connection loops abandon their next read.
     pub shutdown: Arc<Notify>,
     pub shutting_down: Arc<AtomicBool>,
+    /// Global oplock state manager (Phase 2).
+    pub oplock_manager: Arc<crate::oplock::OplockManager>,
 }
 
 impl ServerState {
@@ -208,6 +210,7 @@ impl ServerState {
             server_start_filetime: now_filetime(),
             shutdown: Arc::new(Notify::new()),
             shutting_down: Arc::new(AtomicBool::new(false)),
+            oplock_manager: Arc::new(crate::oplock::OplockManager::new()),
         }
     }