ClearChat Home v1.4.1 - Home Completion Polish

Added:
- Product logo upload support in Settings.
- Admin sidebar logo display.
- PHP upload limit display in Settings and Reliability.
- Automatic avatar/logo resize to 512x512 when PHP GD is available.
- Clearer image upload limit messages.
- Image upload fallback when PHP GD is unavailable.

Notes:
- Avatar/logo uploads are saved in /uploads/avatars/.
- Recommended upload size remains under 2 MB for broad server compatibility.
- Product logo is separate from the agent/avatar image.
