tailscale-proxy: unify HTTP+SOCKS on 3proxy with LAN-free / external-password auth

Retire the tinyproxy HTTP container (tinyproxy has no per-source-IP
conditional auth) and serve both the HTTP proxy (:3128) and SOCKS5 (:1080)
from a single 3proxy instance. LAN (192.168.0.0/22) stays passwordless;
any non-LAN source (i.e. external clients via the router port-forward) must
authenticate. Credentials live in a host-only /etc/3proxy/3proxy.secret
(0600, not in git), included by 3proxy.cfg. A deny rule on the gateway IP
makes the proxy fail closed if the port-forward ever SNATs to 192.168.0.1.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tailscale-proxy/3proxy.cfg

@@ -1,8 +1,47 @@
+# Unified LAN proxy for the tekhnohim Tailscale exit-node egress.
+#
+# One 3proxy instance serves BOTH an HTTP proxy (:3128) and a SOCKS5 proxy
+# (:1080), each chained to the Tailscale userspace SOCKS5 (ts-proxy:1055) so
+# clients exit the internet as the Hetzner exit-node IP (89.167.72.79).
+# TCP only (Tailscale userspace SOCKS5 has no UDP ASSOCIATE -> no QUIC/HTTP3).
+#
+# Access model (LAN free, outside password):
+#   * LAN 192.168.0.0/22  -> authorised by source IP, NO password.
+#   * everyone else       -> must authenticate (external clients arriving via
+#                            the router port-forward keep their public source
+#                            IP, so they fall through to the password rule).
+# The username/password lives in a host-only file (0600, NOT in git), mounted
+# separately and pulled in with the include below - same pattern as ts.env.
+
 nserver 127.0.0.11
 nscache 65536
 timeouts 1 5 30 60 180 1800 15 60
 log
-auth iponly
+
+# Account(s) for external, password-authenticated access (host-only secret):
+include /etc/3proxy/3proxy.secret
+
+# iponly authorises the LAN by address; strong forces login for the rest.
+auth iponly strong
+
+# Safety guard: never treat the router's own address as a trusted LAN client.
+# If the port-forward ever SNATs external traffic to the gateway IP, this rule
+# makes the proxy fail CLOSED (external denied) instead of becoming an open
+# proxy. Verify after opening the port: an unauthenticated external client
+# must be refused.
+deny * 192.168.0.1
+
+# LAN clients: allowed by source IP, no password. Egress via the Tailscale
+# userspace SOCKS5 (a `parent` binds to the `allow` line directly above it).
 allow * 192.168.0.0/22
 parent 1000 socks5 ts-proxy 1055
+
+# External clients: must present the configured account, same egress.
+allow thproxy
+parent 1000 socks5 ts-proxy 1055
+
+# Anything else: denied.
+deny *
+
+proxy -p3128 -a -i0.0.0.0
 socks -p1080 -i0.0.0.0