feat: add FlashStudio and OrcaSlicer 2.4 support

Add FlashStudio slicer support with new SlicerType.FlashStudio enum member
and multi-word name detection in generated-by header parsing.

Add OrcaSlicer 2.4.0-alpha fixture and tests.

Refactor OrcaFlashForgeParser into shared orca-family module:
- OrcaFamilyParser handles all OrcaSlicer-family gcode (OrcaSlicer, Orca-FlashForge, FlashStudio)
- slicer-detection.ts parses generated-by lines and maps to correct SlicerType
- Old OrcaFlashForgeParser.ts re-exports for backward compatibility

Update ThreeMfParser to extract warnings and firstLayerTime from slice_info.config.
Both fields are parsed unconditionally (empty/null when absent).

Rename all test fixtures to include slicer version in filename.
Add test suites for FlashStudio v1.7.6 and OrcaSlicer v2.4.0-alpha.
Remove unused Container 50x50.gcode and regular_orca_test.gcode.backup.

Author: GhostTypes