Integrate backup metrics into system widget with enhanced disk monitoring

Replace standalone backup widget with compact backup section in system widget displaying disk serial, temperature, wear level, timing, and usage information.

Changes:
- Remove standalone backup widget and integrate into system widget
- Update backup collector to read TOML format from backup script
- Add BackupDiskData structure with serial, usage, temperature, wear fields
- Implement compact backup display matching specification format
- Add time formatting utilities for backup timing display
- Update backup data extraction from TOML with disk space parsing

Version bump to v0.1.149

CLAUDE.md

@@ -325,6 +325,12 @@ Storage:
 ● nvme0n1 T: 25C W: 4%
   ├─ ● /: 55% 250.5GB/456.4GB
   └─ ● /boot: 26% 0.3GB/1.0GB
+
+Backup:
+● WD-WCC7K1234567 T: 32°C W: 12%
+  ├─ Last: 2h ago (12.3GB)
+  ├─ Next: in 22h
+  └─ ● Usage: 45% 678GB/1.5TB
 ```
 
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