Bind OP25 control API and terminal to loopback by default

Both :8001 (FastAPI control API) and :8081 (OP25's HTTP terminal) listened on
0.0.0.0 with no authentication, on a container that is privileged with /dev
mounted and network_mode: host. Nodes get deployed to third-party sites, so
that exposed start/stop/retune to anyone on the host's LAN.

All three containers share the host network namespace, so edge-node still
reaches both over 127.0.0.1 unchanged. OP25_DEBUG_EXPOSE=true restores the
old 0.0.0.0 binding and logs a loud warning; it is off by default.

Confirmed against boatbod/op25 gr310 that the terminal's http:<host>:<port>
string is honoured as a real bind address (http_server.py splits it and hands
the host to create_server), so no flag was invented.

Also reorder models.py so IcecastConfig precedes ConfigGenerator, which
annotates a field with it. That only worked because python:slim-trixie is
currently Python 3.14, where PEP 649 defers annotation evaluation; on 3.13 or
earlier the same file is a hard NameError at import.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

op25-container/app/config.py

@@ -0,0 +1,33 @@
+from pydantic_settings import BaseSettings
+
+
+class Settings(BaseSettings):
+    # ------------------------------------------------------------------
+    # OP25_DEBUG_EXPOSE — debugging aid, NOT a deployment mode.
+    #
+    # False (default): the op25 FastAPI control API (:8001, start/stop/
+    # generate-config) and OP25's own HTTP terminal (:8081, live talkgroup
+    # metadata) both bind 127.0.0.1. All three Client containers share the
+    # host network namespace (network_mode: host), so edge-node still reaches
+    # both over localhost with no functional change — nothing off-box can.
+    # Neither surface has authentication, so this is the only thing closing
+    # that hole.
+    #
+    # True: both bind 0.0.0.0 — reachable by anything on the node's LAN with
+    # NO authentication (start/stop OP25, rewrite its config, raw terminal
+    # access). Only ever set this for local development off a real deployed
+    # node. A loud warning naming both ports is logged at startup whenever
+    # this is true.
+    # ------------------------------------------------------------------
+    op25_debug_expose: bool = False
+
+    class Config:
+        env_file = ".env"
+
+
+settings = Settings()
+
+
+def bind_host() -> str:
+    """Resolve the single bind address for both :8001 and :8081 from the flag."""
+    return "0.0.0.0" if settings.op25_debug_expose else "127.0.0.1"