Fix module subprocess lifecycle and capture_bus injection bugs

Three bugs causing all modules to exit within seconds of startup:

1. _module_runner had no keep-alive loop after calling module.start().
   All modules use a thread-spawning pattern where start() returns
   immediately, so the subprocess exited and killed all daemon threads.
   Added while module._running: sleep(1) loop to block until stop().

2. Engine injected capture_bus under key 'capture_bus' but 9 modules
   (auth_flow_tracker, cloud_token_harvester, ldap_harvester, network_mapper,
   rdp_monitor, quic_analyzer, smb_monitor, db_interceptor, vlan_discovery)
   look for '_capture_bus'. Inject both keys so all modules get it.

3. mac_manager crashes on startup when innocuous_macs.db exists but has
   no mac_profiles table (DB not yet seeded). Added OperationalError
   handler to fall back to random OUI instead of crashing.

core/engine.py

@@ -192,11 +192,18 @@ def _module_runner(module_class: Type[BaseModule], bus_queue: multiprocessing.Qu
 
     try:
         module.start()
+        # start() is non-blocking — keep subprocess alive while module threads run
+        while module._running:
+            time.sleep(1)
     except Exception:
         logger.exception("Module %s crashed in start()", module.name)
         bus_proxy.emit("MODULE_ERROR", {"module": module.name, "error": "start_crash"},
                        source_module=module.name)
     finally:
+        try:
+            module.stop()
+        except Exception:
+            pass
         state.stop()
 
 
@@ -357,9 +364,11 @@ class Engine:
                 self.capture_bus = None
         
         # Inject capture_bus into module configs for passive modules
+        # Some modules use "capture_bus", others "_capture_bus" — inject both
         for name, entry in self._modules.items():
             if getattr(entry.module_class, "requires_capture_bus", False):
                 entry.config["capture_bus"] = self.capture_bus
+                entry.config["_capture_bus"] = self.capture_bus
         
         results = {}
         for name in order: