feat: add sharing FastAPI and Django server

[Lenochxd]

This pull request introduces a new FastAPI-based public upload/download API for ShareMii .ltd files, including image preview support, rate limiting, and MySQL-backed metadata storage. It also adds a Django UI server, comprehensive configuration, and documentation. The changes are organized into API implementation, configuration, database and file handling, and developer tooling.

API Implementation and Core Features:

• Introduced a FastAPI app (src/app/main.py) with endpoints for uploading .ltd files (with optional metadata and up to 5 compressed preview images), downloading files and images, and retrieving Mii metadata by share code. All endpoints are rate-limited per client and validate file types, sizes, and identifiers. [1] [2] [3] [4] [5]
• Added in-memory byte-based rate limiting for uploads and downloads, keyed by client IP hash, with 429 responses and retry headers.

Database, File, and Image Handling:

• Added MySQL integration for storing and retrieving Mii metadata and image paths, with initialization from init_db.sql. Image uploads are compressed to JPEG and stored in storage/images. Unique 6-character share codes are generated and validated. [1] [2]
• Added robust file and image validation, including allowed extensions, file size limits, and secure filename checks. [1] [2]

Configuration and Setup:

• Centralized all API, Django, and MySQL configuration in config.json and loaded settings in src/app/settings.py. [1] [2]
• Added a main entrypoint (main.py) that launches both the FastAPI API and the Django UI server concurrently, with proper process management. [1] [2]

Documentation and Developer Tooling:

• Added a detailed API.md with endpoint documentation, usage examples, and configuration notes. Updated the preview image path in README.md. [1] [2]
• Added .gitattributes for line ending normalization and VSCode settings for Python analysis. [1] [2]

Django UI Server:

• Added Django ASGI setup and management scripts for the ShareMii web UI, integrated with the FastAPI backend. [1] [2]

These changes together provide a robust, configurable, and well-documented backend for ShareMii file sharing, supporting both programmatic API access and a web UI.

(PR description written by copilot)

[Lenochxd]

Todo:

• (CI)/CD
• remove github pages
• configure cloudflare