Add configurable occupied/clear delays with extended 5-minute range

[Chris971991]

Summary

This PR introduces user-configurable delay settings for bed occupancy detection, allowing independent control over "occupied" and "clear" state transitions with an extended range of 0-300 seconds (5 minutes).

What's Changed

• ✨ Added configurable "Occupied Delay" and "Clear Delay" for each sensor side (Left/Right)
• ⏱️ Extended delay range from fixed presets to 0-300 seconds (0-5 minutes)
• 🎛️ Added "Custom" option to Response Speed selector
• 📊 Created separate number entities for fine-grained control (0.5s steps)
• 📝 Added comprehensive documentation

Why This Feature?

Users needed more flexibility than the fixed Fast/Normal/Slow presets to:

• Prevent false positives when briefly sitting on the bed
• Prevent false negatives during restless sleep
• Customize delays based on individual sleep patterns
• Support advanced automations requiring longer confirmation periods

Key Benefits

• Flexible Configuration: 0-300 second range (5 minutes max)
• Independent Control: Separate delays for occupied vs clear states
• Per-Side Settings: Left and right sensors can have different delays
• Backward Compatible: Existing modes remain unchanged
• Persistent Settings: Values survive restarts

Files Modified

• bed-presence-mk1/sensor.yaml - Core implementation
• bed-presence-mk1/base.yaml - Added "Custom" response speed
• bed-presence-mk1.yaml - Added inline documentation

Breaking Changes

None - Fully backward compatible

Testing Checklist

• YAML validation passes
• Backward compatibility verified
• Hardware testing completed