[FEATURE]: Footer lacks information about AOSSIE and useful project links

### Feature and its Use Cases

The current footer only shows a Discord icon and the text "Made with love by AOSSIE team". Visitors who are unfamiliar with AOSSIE have no context about the organisation behind PictoPy, and there are no links to key resources like documentation, the GitHub repo, release downloads, or community channels.

Expected behaviour

The footer should:

Include a brief description of AOSSIE and a link to aossie.org
Provide quick links to Docs, Releases, Issue Tracker, and Contributing Guide
Surface community links (Discord, GitHub, Twitter)
Show a proper copyright notice with the current year
Current behaviour

Footer is a single line: Discord icon + "Made with love by AOSSIE team"

Suggested solution
Replace with a responsive multi-column layout that covers the brand, organisation background, quick links, and community — consistent with the existing yellow→green design system and dark mode support.

### Additional Context

_No response_

### Code of Conduct

- [x] I have joined the [Discord server](https://discord.gg/hjUhu33uAn) and will post updates there
- [x] I have searched existing issues to avoid duplicates