feat: initial IRC bouncer implementation

Async Python IRC bouncer with SOCKS5 proxy support, multi-network
connections, password auth, and persistent SQLite backlog with replay.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

PROJECT.md

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+# Project: bouncer
+
+## Purpose
+
+IRC bouncer that maintains persistent connections to IRC servers through a SOCKS5 proxy, allowing IRC clients to connect/disconnect while keeping the session alive and replaying missed messages.
+
+## Architecture
+
+```
+IRC Client(s) --> [bouncer:6667] --> Router --> [SOCKS5:1080] --> IRC Server(s)
+                                      |
+                                   Backlog
+                                  (SQLite)
+```
+
+### Components
+
+| Module | Responsibility |
+|--------|---------------|
+| `irc.py` | IRC protocol parser/formatter (RFC 2812 subset) |
+| `config.py` | TOML configuration loading and validation |
+| `proxy.py` | SOCKS5 async connection wrapper |
+| `network.py` | Persistent IRC server connection per network |
+| `server.py` | TCP listener accepting IRC client connections |
+| `client.py` | Per-client session and IRC handshake |
+| `router.py` | Message routing between clients and networks |
+| `backlog.py` | SQLite message storage and replay |
+
+### Key Decisions
+
+- **asyncio**: Single-threaded async for all I/O
+- **python-socks**: Async SOCKS5 proxy support
+- **aiosqlite**: Non-blocking SQLite for backlog
+- **No IRC library**: Manual protocol handling (IRC is simple line-based)
+
+## Dependencies
+
+| Package | Version | Purpose |
+|---------|---------|---------|
+| python-socks[asyncio] | >=2.4 | SOCKS5 proxy |
+| aiosqlite | >=0.19 | Async SQLite |
+
+## Requirements
+
+- Python 3.10+
+- SOCKS5 proxy running on 127.0.0.1:1080