Add hat cog for festive Christmas avatar overlays

[Copilot]

• Create new hat cog directory structure (__init__.py, hat.py, info.json)
• Implement core Hat cog class with Config for user data storage
• Implement user commands under .hat group:
  • .hat list - List available hats
  • .hat select <name> - Select a hat with live preview
  • .hat scale <value> - Adjust hat size with live preview
  • .hat rotate <degrees> - Adjust hat rotation with live preview
  • .hat position <x> <y> - Adjust hat position with live preview
  • .hat reset - Reset to defaults with live preview
  • .hat show - Refresh preview with current avatar
• Implement admin commands under .sethat group:
  • .sethat upload <name> - Upload a new hat image
  • .sethat remove <name> - Remove a hat
  • .sethat list - List all hats with admin info
  • .sethat default <name> - Set default hat
• Live previews after every adjustment command
• Auto-cleanup of command messages after 3 seconds
• Previous preview cleanup when showing new one
• Implicit settings saving (removed save/load commands)
• Proper task tracking for cog unload cleanup
• Add Pillow>=10.2.0 dependency for image manipulation
• Update README.md documentation
• Update copilot-instructions.md
• Run code review and address feedback
• Run security scan (passed)

Original prompt

create a new cog called "hat".

the goal of this cog should be to help users create a more festive version of their avatar by overlaying a Christmas hat on top of their existing avatar.

users should be able to select from multiple hats, along with changing the scale, rotation and placement.

users should be able to save and reuse in the future.

user commands should be under .hat, with any admin commands under .sethat

commands should be available in a guild or DM

admins should be able to upload and manage existing hats via commands

the bot should attempt to keep channels clean by deleting previous commands from users

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[psykzz]

@copilot Message cleanup seems to happen only on the next command should happen a few seconds after running any command. As a user runs .hat scale 1, 3 seconds late the message should be deleted. We should not wait until the next command. The bot should also preview the hat after every command instead of on preview, or apply, The bot should only show teh latest hat, so it should cleanup previous previews for a specific user when showing a new one. apply and preview don't really make sense anymore if we have "live" previews. save and load should also be implicit with the changes always be saved after use .hat show could be used to show the current image if some time has passed and users want to apply the hat to a new avatar

[Copilot]

@copilot Message cleanup seems to happen only on the next command should happen a few seconds after running any command. As a user runs .hat scale 1, 3 seconds late the message should be deleted. We s...

Implemented all requested changes in 319b778:

• Live previews: Every adjustment command (select, scale, rotate, position, reset) now automatically shows a live preview
• Auto-cleanup: Command messages delete after 3 seconds, not on next command
• Previous preview cleanup: Old previews are deleted when showing new ones
• Added .hat show: Refreshes the preview for users who want to see it again or after changing their avatar
• Removed preview, apply, save, load, settings: No longer needed with live previews
• Implicit saving: Settings are stored automatically after each change

Tasks are properly tracked and cancelled on cog unload to prevent orphaned tasks.