docs: add public documentation for contributors and users

Created 12 public docs derived from internal vault:
- Setup guides: quick-start, server-configuration, livekit-setup, deployment
- Networking: port-forwarding, tailscale
- References: api, protocol, schema, client-architecture
- Community: contributing, security

Updated .gitignore to only exclude docs/brain/ (internal vault),
allowing docs/ to be tracked. Updated README with expanded quick
start, voice/video setup, networking ports, and doc links.

docs/tailscale.md

@@ -0,0 +1,23 @@
+# Tailscale Guide (Zero-Config Alternative)
+
+Use Tailscale for secure, zero-config networking without port forwarding.
+
+## What is Tailscale
+
+Tailscale is a mesh VPN that creates encrypted tunnels between your devices using WireGuard. No port forwarding, no dynamic DNS, and it works behind CGNAT. Free for personal use.
+
+## Setup
+
+1. **Install Tailscale** on the server machine and each client machine: https://tailscale.com/download
+2. **Sign in** with the same Tailscale account (or share the machine using Tailscale's sharing feature)
+3. **Find the server's Tailscale IP** -- shown in the Tailscale app, typically `100.x.y.z`
+4. **Disable TLS in config** -- set `tls.mode` to `"off"` in `config.yaml` since Tailscale already encrypts all traffic with WireGuard
+5. **Connect clients** using the Tailscale IP: `100.x.y.z:8443`
+
+## Benefits
+
+- No port forwarding needed
+- Works behind CGNAT and strict firewalls
+- Encrypted by default (WireGuard)
+- Stable IPs that don't change
+- Easy to add/remove friends via the Tailscale admin console