fix: make the SOCKS5 proxy work for BookMyShow too

BookMyShow blocks datacenter IPs on top of TLS fingerprinting, confirmed by CI
runners getting 403 with a working impersonation, so cloud hosts need the proxy
for BMS as well as District. impit resolves DNS locally for socks5:// and hands
an IPv6-only exit an unreachable IPv4 address, so the scheme is normalized to
socks5h://. Verified end to end: a proxied BMS check returns 200 and alerts.

Docs said the proxy did nothing for BookMyShow, which was wrong.

.env.example

@@ -60,7 +60,8 @@ CURRENCY=₹
 STATE_PATH=./state.json        # Docker image defaults this to /data/state.json
 PORT=4733                      # status endpoint (--loop mode only)
 
-# Routes District checks through a SOCKS5 proxy; notifications stay direct.
-# Needed on datacenter hosts, whose IPs District's WAF blocks. It does nothing for
-# BookMyShow, which blocks on TLS fingerprint rather than IP (impit handles that).
+# Routes both sites' checks through a SOCKS5 proxy; notifications stay direct.
+# Both District and BookMyShow block datacenter IPs, so a cloud host usually needs this.
+# socks5:// is rewritten to socks5h:// internally, so the proxy resolves DNS. That is
+# required for IPv6-only exits and harmless otherwise.
 # PROXY_URL=socks5://user:pass@proxy.example.net:1080