Addresses audit findings A001, T002:
A001 - Undefined Plugin Interface:
- Created src/plugins/interface.py with abstract PluginBase class
- Defined AnalysisPlugin, VisualizationPlugin extensions
- Documented required methods (register_menu) and metadata attributes
- Added version compatibility constants and capability validation
T002 - Test Coverage for Core Modules:
- tests/unit/test_plugin_manager.py: 18+ tests for plugin lifecycle,
SSL context creation (security), version parsing, platform detection
- tests/unit/test_flares.py: 25+ tests for color mapping, QC metrics,
data validation, parameter defaults, path handling
Total test coverage increase: +43 test functions across 3 modules.
