core: bind a raw-TCP service as <name>.<domain>:<port>

A `{ref, bind}` to a TCP-exposed deployment (e.g. postgres) projected
nothing, so consumers hardcoded the docker bridge IP. Project the address
it's already documented as reachable at.

core/src/wildpc_core/deploy.py

@@ -682,6 +682,11 @@ def _target_url(config: WildpcConfig, target_name: str) -> str | None:
     base = getattr(dep, "base_url", None)
     if base:
         return base
+    # A raw-TCP service has no URL scheme — project its `host:port`, reachable
+    # through wildcard DNS (see docs/tcp-exposure.md).
+    tcp_port = getattr(dep, "tcp_port", None)
+    if tcp_port and config.gateway.domain:
+        return f"{target_name}.{config.gateway.domain}:{tcp_port}"
     expose = getattr(dep, "expose", None)
     http = getattr(expose, "http", None) if expose else None
     tport = http.internal.port if http else None