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/USAGE.md

@@ -0,0 +1,77 @@
+# Usage
+
+## Starting the Bouncer
+
+```bash
+bouncer -c config/bouncer.toml -v
+```
+
+| Flag | Description |
+|------|-------------|
+| `-c, --config PATH` | Config file (default: `config/bouncer.toml`) |
+| `-v, --verbose` | Debug logging |
+| `--version` | Show version |
+
+## Connecting with an IRC Client
+
+Configure your IRC client to connect to the bouncer:
+
+| Setting | Value |
+|---------|-------|
+| Server | `127.0.0.1` |
+| Port | `6667` (or as configured) |
+| Password | `networkname:yourpassword` |
+
+### Password Format
+
+```
+PASS <network>:<password>
+```
+
+- `network` -- matches a `[networks.NAME]` section in config
+- `password` -- the `bouncer.password` value from config
+
+If you omit the network prefix (`PASS yourpassword`), the first configured network is used.
+
+### Client Examples
+
+**irssi:**
+```
+/connect -password libera:mypassword 127.0.0.1 6667
+```
+
+**weechat:**
+```
+/server add bouncer 127.0.0.1/6667 -password=libera:mypassword
+/connect bouncer
+```
+
+**hexchat:**
+Set server password to `libera:mypassword` in the network settings.
+
+## Multiple Networks
+
+Define multiple `[networks.*]` sections in the config. Connect with different passwords to access each:
+
+```
+PASS libera:mypassword    # connects to libera
+PASS oftc:mypassword      # connects to oftc
+```
+
+Multiple clients can attach to the same network simultaneously.
+
+## Backlog
+
+Messages are stored in `bouncer.db` (SQLite) next to the config file. When you reconnect, missed messages are automatically replayed.
+
+Configure backlog in `bouncer.toml`:
+
+```toml
+[bouncer.backlog]
+max_messages = 10000       # per network, 0 = unlimited
+replay_on_connect = true   # set false to disable replay
+```
+
+## Stopping
+
+Press `Ctrl+C` or send `SIGTERM`. The bouncer shuts down gracefully.