Defines the `StorageBackend` abstract base class with a uniform interface for loading and saving account data, configuration, and other persisted objects. Concrete implementations for JSON files, SQLite/PostgreSQL (via `database_storage.py`), and Git-backed storage each conform to this interface. This pattern allows easy swapping of storage backends without affecting business logic, and is reusable in any project needing pluggable persistence.

Implements a thread-safe cache for chat completions with deduplication of in-flight requests (coalescing identical concurrent calls) and TTL-based response caching. Handles both streaming and non-streaming responses, normalizes messages to generate cache keys, and tracks cached tokens in usage statistics. This is a clean, reusable caching solution for any API that serves completion-style responses.

Provides a runtime proxy configuration system with support for multiple proxy profiles (WARP, FlareSolverr, custom HTTP/HTTPS/SOCKS5). Includes a Cloudflare clearance mechanism that caches clearance tokens (cookies, user-agent) with single-flight deduplication to avoid redundant FlareSolverr calls. The `ProxyRuntimeSettings` model is serializable and can be dynamically updated. This is a reusable pattern for any application that needs to route requests through configurable proxies with bypass capabilities.

Contains a collection of well-isolated utility functions for image validation (MIME type, size, base64/URL decoding), SSE streaming helpers (`sse_json_stream`, `anthropic_sse_stream`), and common data transformations (token anonymization, prompt extraction). Each function is self-contained, fully parameterized, and can be extracted into any Python project requiring image processing or SSE handling.