fix: Update panic handler for V4-engine API changes

- Update panic_handler.cpp to use V4PanicInfo struct
- Use PRId32 format specifier for portable int32_t formatting
- Add missing LED control functions
- Add <cinttypes> include for PRId32
- Re-enable panic_handler.cpp in build configuration
- Fix Docker compose V4-engine mount path (V4 → V4-engine)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: kirisaki

CHANGELOG.md

@@ -7,6 +7,19 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+- **Updated panic handler for V4-engine Unreleased API**
+  - Use `V4PanicInfo` struct with new field names
+  - Use `PRId32` format specifier for portable int32_t formatting
+  - Re-enabled panic_handler.cpp in build configuration
+  - Fixed Docker compose V4-engine mount path (V4 → V4-engine)
+
+### Fixed
+- Fixed compilation errors in panic handler implementation
+  - Added missing LED control functions
+  - Added `<cinttypes>` include for PRId32
+  - Corrected PanicInfo field access
+
 ## [0.3.0] - 2025-11-05
 
 ### Added