v2.1.1 - Config Flow Fixes

What's Fixed

Timestamp Sensor Bug

• last_spot sensor now returns proper datetime with UTC timezone
• Fixes 'str' object has no attribute 'tzinfo' error

Options Flow 500 Error

• Fixed AttributeError: property 'config_entry' has no setter
• Updated to modern HA OptionsFlow pattern (no manual config_entry assignment)
• Fixed invalid multi-select syntax for mode filter

Improved Setup Flow

• Two-step configuration: choose monitor type first (Personal/Global)
• Global monitor skips callsign/direction (not applicable)
• Personal monitor shows callsign + direction step
• Mode filter uses proper dropdown multi-select UI

Full Changelog: v2.1.0...v2.1.1