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/conn/state.rs

@@ -294,6 +294,9 @@ pub struct Open {
     pub is_directory: bool,
     pub delete_on_close: bool,
     pub search_state: Option<DirCursor>,
+    // Oplock fields (MS-SMB2 §2.2.13 / §2.2.14)
+    pub oplock_level: u8,
+    pub share_access: u32,
 }
 
 impl Open {
@@ -304,6 +307,8 @@ impl Open {
         last_path: SmbPath,
         is_directory: bool,
         delete_on_close: bool,
+        oplock_level: u8,
+        share_access: u32,
     ) -> Self {
         Self {
             file_id,
@@ -313,6 +318,8 @@ impl Open {
             is_directory,
             delete_on_close,
             search_state: None,
+            oplock_level,
+            share_access,
         }
     }
 }