feat: replace bind-mount log pipeline with Docker log streaming

Services now print RFC 5424 to stdout; Docker captures via json-file driver.
A new host-side collector (decnet.web.collector) streams docker logs from all
running decky service containers and writes RFC 5424 + parsed JSON to the host
log file. The existing ingester continues to tail the .json file unchanged.
rsyslog can consume the .log file independently — no DECNET involvement needed.

Removes: bind-mount volume injection, _LOG_NETWORK bridge, log_target config
field and --log-target CLI flag, TCP syslog forwarding from service templates.

decnet/composer.py

@@ -6,6 +6,12 @@ Network model:
   All service containers for that decky share the base's network namespace
   via `network_mode: "service:<base>"`.  From the outside, every service on
   a given decky appears to come from the same IP — exactly like a real host.
+
+Logging model:
+  Service containers write RFC 5424 lines to stdout.  Docker captures them
+  via the json-file driver.  The host-side collector (decnet.web.collector)
+  streams those logs and writes them to the host log file for the ingester
+  and rsyslog to consume.  No bind mounts or shared volumes are needed.
 """
 
 from pathlib import Path
@@ -17,38 +23,19 @@ from decnet.network import MACVLAN_NETWORK_NAME
 from decnet.os_fingerprint import get_os_sysctls
 from decnet.services.registry import get_service
 
-_CONTAINER_LOG_DIR = "/var/log/decnet"
-
-_LOG_NETWORK = "decnet_logs"
-
-
-def _resolve_log_file(log_file: str) -> tuple[str, str]:
-    """
-    Return (host_dir, container_log_path) for a user-supplied log file path.
-
-    The host path is resolved to absolute so Docker can bind-mount it.
-    All containers share the same host directory, mounted at _CONTAINER_LOG_DIR.
-    """
-    host_path = Path(log_file).resolve()
-    host_dir = str(host_path.parent)
-    container_path = f"{_CONTAINER_LOG_DIR}/{host_path.name}"
-    return host_dir, container_path
+_DOCKER_LOGGING = {
+    "driver": "json-file",
+    "options": {
+        "max-size": "10m",
+        "max-file": "5",
+    },
+}
 
 
 def generate_compose(config: DecnetConfig) -> dict:
     """Build and return the full docker-compose data structure."""
     services: dict = {}
 
-    log_host_dir: str | None = None
-    log_container_path: str | None = None
-    if config.log_file:
-        log_host_dir, log_container_path = _resolve_log_file(config.log_file)
-        # Ensure the host log directory exists and is writable by the container's
-        # non-root 'decnet' user (DEBT-019).  mkdir respects umask, so chmod explicitly.
-        _log_dir = Path(log_host_dir)
-        _log_dir.mkdir(parents=True, exist_ok=True)
-        _log_dir.chmod(0o777)
-
     for decky in config.deckies:
         base_key = decky.name  # e.g. "decky-01"
 
@@ -65,8 +52,6 @@ def generate_compose(config: DecnetConfig) -> dict:
                 }
             },
         }
-        if config.log_target:
-            base["networks"][_LOG_NETWORK] = {}
 
         # Inject TCP/IP stack sysctls to spoof the claimed OS fingerprint.
         # Only the base container needs this — service containers inherit the
@@ -80,9 +65,7 @@ def generate_compose(config: DecnetConfig) -> dict:
         for svc_name in decky.services:
             svc = get_service(svc_name)
             svc_cfg = decky.service_config.get(svc_name, {})
-            fragment = svc.compose_fragment(
-                decky.name, log_target=config.log_target, service_cfg=svc_cfg
-            )
+            fragment = svc.compose_fragment(decky.name, service_cfg=svc_cfg)
 
             # Inject the per-decky base image into build services so containers
             # vary by distro and don't all fingerprint as debian:bookworm-slim.
@@ -91,12 +74,6 @@ def generate_compose(config: DecnetConfig) -> dict:
 
             fragment.setdefault("environment", {})
             fragment["environment"]["HOSTNAME"] = decky.hostname
-            if log_host_dir and log_container_path:
-                fragment["environment"]["DECNET_LOG_FILE"] = log_container_path
-                fragment.setdefault("volumes", [])
-                mount = f"{log_host_dir}:{_CONTAINER_LOG_DIR}"
-                if mount not in fragment["volumes"]:
-                    fragment["volumes"].append(mount)
 
             # Share the base container's network — no own IP needed
             fragment["network_mode"] = f"service:{base_key}"
@@ -106,6 +83,9 @@ def generate_compose(config: DecnetConfig) -> dict:
             fragment.pop("hostname", None)
             fragment.pop("networks", None)
 
+            # Rotate Docker logs so disk usage is bounded
+            fragment["logging"] = _DOCKER_LOGGING
+
             services[f"{decky.name}-{svc_name}"] = fragment
 
     # Network definitions
@@ -114,8 +94,6 @@ def generate_compose(config: DecnetConfig) -> dict:
             "external": True,  # created by network.py before compose up
         }
     }
-    if config.log_target:
-        networks[_LOG_NETWORK] = {"driver": "bridge", "internal": True}
 
     return {
         "version": "3.8",