fix: show the container hostname in the shell prompt

Coolify injects HOST=0.0.0.0 into every compose app, and zsh seeds $HOST and
the %m/%M prompt escapes from that variable rather than calling gethostname().
The prompt read "0", the first dot-separated field of 0.0.0.0, even though the
container hostname itself was set correctly.

Pass the hostname in as HOST alongside the hostname: key, both from a single
SERVICE_HOSTNAME variable. Neither service reads HOST itself -- code-server
binds [::]:8443, Paseo binds PASEO_LISTEN -- so this only affects the prompt.

Not named HOSTNAME: Compose interpolation lets the deploying shell's
environment win over the .env file, and HOSTNAME is set in every container,
including the one Coolify runs in.

PASEO_LABEL is renamed to SERVICE_HOSTNAME; it was never a Paseo variable.
The example git identity is blanked out along with it.

paseo/.env.example

@@ -18,8 +18,10 @@ PASEO_HOSTNAMES=
 PASEO_TRUSTED_PROXIES=uniquelocal
 
 # Container hostname, shown as the host label in the web UI. Without it the
-# label is a random container ID.
-PASEO_LABEL=paseo
+# label is a random container ID. Also passed in as HOST -- the name zsh's
+# prompt shows. Not named HOSTNAME: the deploying shell's own HOSTNAME would
+# override it.
+SERVICE_HOSTNAME=paseo
 
 # Agent CLIs to install on start, if not already present. Space- or
 # comma-separated, from: claude codex opencode copilot omp pi. Leave empty to
@@ -32,8 +34,8 @@ TZ=Asia/Ho_Chi_Minh
 
 # Git identity for agents and terminals, as author and committer. git reads
 # these directly, so no `git config` step is needed.
-GIT_NAME=tiennm99
-GIT_EMAIL=tiennm99@outlook.com
+GIT_NAME=
+GIT_EMAIL=
 
 # Shell for Paseo's terminals. Paseo reads $SHELL and otherwise falls back to
 # /bin/sh (dash); it ignores the user's login shell, so `chsh` has no effect.