Add admin system, registration gate, mudtool database editor, and test checklist

- Add is_admin flag to player DB schema with migration for existing databases
- Add server_settings table for key-value config (registration_open, etc.)
- Add 10 in-game admin commands: promote, demote, kick, teleport, registration,
  announce, heal, info, setattitude, list — all gated behind admin flag
- Registration gate: new players rejected when registration_open=false,
  existing players can still reconnect
- Add mudtool binary with CLI mode (players/settings/attitudes CRUD) and
  interactive ratatui TUI with tabbed interface for database management
- Restructure to lib.rs + main.rs so mudtool shares DB code with server
- Add TESTING.md with comprehensive pre-commit checklist and smoke test script
- Stats and who commands show [ADMIN] badge; help shows admin section for admins

Made-with: Cursor

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "mudserver"
-version = "0.1.0"
+version = "0.2.0"
 edition = "2021"
 
 [dependencies]
@@ -10,5 +10,7 @@ serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 toml = "0.8"
 rusqlite = { version = "0.35", features = ["bundled"] }
+ratatui = "0.30"
+crossterm = "0.28"
 log = "0.4"
 env_logger = "0.11"