docs: add SoundTouch 30 factory reset sequence (#305)

## Description

Add missing factory reset sequence for SoundTouch 30 (non-Series III).
The current table only lists SoundTouch 30 Series III. The SoundTouch 30
uses a different sequence: power on, then hold Preset 1 + Volume − for
10 s. The display counts down from 10 to 1 and shows "Hold to restore
factory settings" before restarting.

## Type of Change

Please check the type of change your PR introduces:

- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [x] Documentation update
- [ ] Performance improvement
- [ ] Code refactoring (no functional changes)
- [ ] Test improvements
- [ ] Build/CI improvements

## Related Issues

## Changes Made

### API Changes
- [ ] Added new endpoints
- [ ] Modified existing endpoints
- [ ] Added new CLI commands
- [ ] Modified existing CLI commands
- [ ] Added new configuration options

### Implementation Details
- Added missing table row for SoundTouch 30 (non-Series III) in the
factory reset sequences table. No new dependencies.

## Testing

### Automated Tests
- [ ] Unit tests added/updated
- [ ] Integration tests added/updated
- [ ] All existing tests pass
- [ ] Test coverage maintained or improved

### Manual Testing
- [x] Tested with real SoundTouch device(s)
- [ ] Tested CLI changes manually
- [ ] Tested in different network environments

**Device(s) tested with:**
- Device model: SoundTouch 30
- Firmware: 27.0.6.46330
- Test results: Factory reset sequence verified on real device

### Test Commands

## Documentation

- [ ] Updated relevant documentation
- [ ] Added code comments for complex logic
- [ ] Updated CLI help text
- [ ] Added usage examples
- [ ] Updated API documentation

**Documentation files updated:**
- [ ] README.md
- [ ] docs/API-Endpoints-Overview.md
- [ ] docs/CLI-REFERENCE.md
- [ ] Code documentation (godoc)

docs/DEVICE-INITIAL-SETUP.md

## Backward Compatibility

- [x] This change is backward compatible
- [ ] This change includes breaking changes (requires major version
bump)
- [ ] This change requires configuration migration

**Breaking changes (if any):**

## Security Considerations

- [x] No security implications
- [ ] Security review required
- [ ] Added input validation
- [ ] Updated authentication/authorization

## Performance Impact

- [x] No performance impact
- [ ] Performance improvement
- [ ] Potential performance regression (justify why)

**Performance notes:**

## Code Quality

- [ ] Code follows project style guidelines
- [ ] No linting errors
- [ ] No security warnings
- [ ] Memory leaks checked (if applicable)

### Pre-submission Checklist

- [ ] `make check` passes (format, lint, vet)
- [ ] `make test` passes
- [ ] No TODO comments left in production code
- [ ] Error handling is comprehensive
- [ ] Logging is appropriate (not too verbose, not too quiet)

## Deployment Notes

## Screenshots (if applicable)

## Additional Notes

## Review Requests

docs/guides/DEVICE-INITIAL-SETUP.md

@@ -86,6 +86,7 @@ A factory reset wipes Wi-Fi credentials, account pairing, and all presets, retur
 | SoundTouch 10            | Power on; hold **Preset 1** + **Volume −** for 10 s                 | Wi-Fi indicator glows solid amber  |
 | SoundTouch 20            | Power on; hold **Preset 1** + **Volume −** for 10 s                 | Lights blink L→R, then solid amber |
 | SoundTouch 20 Series III | Hold **Preset 1** + **Preset 6** simultaneously for ~10 s           | White LED sweep                    |
+| SoundTouch 30            | Power on; hold **Preset 1** + **Volume −** for 10 s (display counts down 10–1) | Display shows "Hold to restore factory settings", then restarts |
 | SoundTouch 30 Series III | Hold **Preset 1** + **Preset 6** simultaneously for ~10 s           | White LED sweep                    |
 | SoundTouch 300           | Hold **Volume −** until light bar blinks rapidly (~15 s)            | Rapid blink → off → on             |
 | SoundTouch 10 (alt)      | Press and hold the back recessed **Reset** pinhole for 10 s         | Status LED restarts                |