Add metadata display and optimize CPU usage

Metadata features:
- Display artist, album, title in bottom status bar (left-aligned)
- Display bitrate, codec, sample rate in bottom status bar (right-aligned)
- Fetch metadata from MPV using metadata/by-key properties
- Support both lowercase and uppercase metadata tags

Performance optimizations:
- Split property updates: fast updates (position/duration) vs slow (metadata)
- Update metadata only every 2 seconds instead of every 100ms
- Skip MPV property updates entirely when stopped
- Conditional UI redraws - only when state actually changes
- Variable poll rate: 200ms when stopped, 100ms when playing
- Position update throttling (0.5s minimum change)
- Reduces CPU usage from constant 10 FPS to ~0.1 FPS when idle

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cm-player"
-version = "0.1.9"
+version = "0.1.10"
 edition = "2021"
 
 [dependencies]