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>

docs/CHEATSHEET.md

@@ -0,0 +1,53 @@
+# Cheatsheet
+
+## Commands
+
+```bash
+bouncer -c config/bouncer.toml       # Start with config
+bouncer -c config/bouncer.toml -v    # Start with debug output
+bouncer --version                    # Show version
+bouncer --help                       # Show help
+```
+
+## Development
+
+```bash
+make dev      # Install with dev deps
+make test     # Run pytest
+make lint     # Run ruff
+make fmt      # Format with black + ruff
+make run      # Run with default config
+make clean    # Remove .venv and build artifacts
+```
+
+## Client Connection
+
+```
+PASS <network>:<password>     # Authenticate + select network
+PASS <password>               # Authenticate, use first network
+```
+
+## Config Structure
+
+```toml
+[bouncer]                     # Listener settings
+  bind / port / password
+  [bouncer.backlog]           # Backlog settings
+    max_messages / replay_on_connect
+
+[proxy]                       # SOCKS5 proxy
+  host / port
+
+[networks.<name>]             # IRC server (repeatable)
+  host / port / tls
+  nick / user / realname
+  channels / autojoin / password
+```
+
+## Files
+
+| Path | Purpose |
+|------|---------|
+| `config/bouncer.toml` | Active configuration |
+| `config/bouncer.db` | SQLite backlog database |
+| `config/bouncer.example.toml` | Example config template |