Implement simple status polling with enhanced printer monitoring (Issue #16)

[krjordan]

Summary

• Implement comprehensive Bambu Labs printer status parsing with actual field names (nozzle_temper, bed_temper, mc_remaining_time)
• Add real-time temperature monitoring and layer progress tracking
• Fix print state inference when explicit state field not available
• Enhance status display with WiFi signal strength and remaining time formatting
• Add device info display for system messages (model, serial number, firmware version)
• Update documentation with monitor output examples and enhanced test coverage

Changes Made

• Enhanced message parsing: Added support for actual Bambu Labs field names in src/messages/mod.rs
• Improved status display: Enhanced printer status output with temperatures, layers, and timing in src/main.rs
• State inference: Fixed "Unknown('no_state')" errors by inferring print state from available data
• Device info display: Added comprehensive device information parsing from system messages
• Documentation updates: Updated README.md and ROADMAP.md to reflect completed features

Test Coverage

• Added test for Bambu Labs actual message format parsing
• Added test for device information extraction from system messages
• All existing tests continue to pass (50 total tests)

Example Output

🖨️ Print Status: Printing - Remaining: 16m 55s
🖨️ Printer Status: 🌡️ Nozzle: 219.8°C | 🛏️ Bed: 45.0°C | 📄 Layer: 10 | ⏱️ Remaining: 16m | 📶 WiFi: -30dBm

Test Plan

• All unit tests pass (34 tests)
• All integration tests pass (16 tests)
• Code formatting and linting checks pass
• Real printer testing with actual Bambu Labs printers confirmed working
• Temperature monitoring displays correctly
• Print state inference works when explicit state not provided
• Device information extraction from system messages works

Closes #16