Replace libmpv with MPV IPC subprocess approach

- Remove libmpv dependency to avoid version mismatch issues
- Spawn mpv as subprocess with --input-ipc-server
- Communicate via Unix socket with JSON IPC protocol
- Add update_properties() to poll MPV state
- No linking required, only mpv binary needed at runtime
- More stable and portable across MPV versions

Cargo.toml

@@ -20,8 +20,8 @@ toml = "0.8"
 walkdir = "2.5"
 dirs = "5.0"
 
-# MPV player
-libmpv = "2.0"
+# MPV player (via IPC)
+tempfile = "3.14"
 
 # Error handling
 anyhow = "1.0"