refactor: wire all services through ApplicationContext

- Created src/application_context.py as DI container with TYPE_CHECKING imports
- server.py now instantiates all services in dependency order via ApplicationContext
- Fixed infinite recursion bug: 48 instance methods renamed with underscore prefix
  to avoid shadowing by same-named @classmethod forwarders
- ZeroconfServer: instantiate Zeroconf() in __init__, add _sync_class() to
  configure forwarder, direct _configure/_start calls during wiring
- Config, EngineManager, PreviewManager: all forwarders and _sync_class() intact
- RenderQueue: load_state and subscribe moved to __init__, threading.Lock retained
- DistributedJobManager: subscribe_to_listener moved to __init__

src/application_context.py

@@ -0,0 +1,25 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING, Optional
+
+if TYPE_CHECKING:
+    from src.api.preview_manager import PreviewManager
+    from src.api.serverproxy_manager import ServerProxyManager
+    from src.distributed_job_manager import DistributedJobManager
+    from src.engines.engine_manager import EngineManager
+    from src.render_queue import RenderQueue
+    from src.utilities.config import Config
+    from src.utilities.zeroconf_server import ZeroconfServer
+
+
+class ApplicationContext:
+    """Holds all service instances. Single source of truth for wiring."""
+
+    def __init__(self) -> None:
+        self.config: Optional[Config] = None
+        self.engine_manager: Optional[EngineManager] = None
+        self.preview_manager: Optional[PreviewManager] = None
+        self.zeroconf_server: Optional[ZeroconfServer] = None
+        self.render_queue: Optional[RenderQueue] = None
+        self.distributed_job_manager: Optional[DistributedJobManager] = None
+        self.server_proxy_manager: Optional[ServerProxyManager] = None