refactor(logging): preserve tracebacks and add channel context

- Preserve tracebacks: logger.error in except blocks → logger.exception
- Channel context: BaseChannel injects self.logger = logger.bind(channel=name)
- Third-party bridge: redirect_lib_logging() replaces ad-hoc stdlib-to-loguru bridges
- Log levels: network timeouts downgraded from ERROR → WARNING
- Fix --verbose flag to actually work with loguru (set handler to DEBUG)

nanobot/channels/base.py

@@ -38,6 +38,7 @@ class BaseChannel(ABC):
             bus: The message bus for communication.
         """
         self.config = config
+        self.logger = logger.bind(channel=self.name)
         self.bus = bus
         self._running = False
 
@@ -61,8 +62,8 @@ class BaseChannel(ABC):
                     language=self.transcription_language or None,
                 )
             return await provider.transcribe(file_path)
-        except Exception as e:
-            logger.warning("{}: audio transcription failed: {}", self.name, e)
+        except Exception:
+            self.logger.exception("Audio transcription failed")
             return ""
 
     async def login(self, force: bool = False) -> bool:
@@ -136,7 +137,7 @@ class BaseChannel(ABC):
         else:
             allow_list = getattr(self.config, "allow_from", [])
         if not allow_list:
-            logger.warning("{}: allow_from is empty — all access denied", self.name)
+            self.logger.warning("allow_from is empty — all access denied")
             return False
         if "*" in allow_list:
             return True
@@ -165,10 +166,10 @@ class BaseChannel(ABC):
             session_key: Optional session key override (e.g. thread-scoped sessions).
         """
         if not self.is_allowed(sender_id):
-            logger.warning(
-                "Access denied for sender {} on channel {}. "
+            self.logger.warning(
+                "Access denied for sender {}. "
                 "Add them to allowFrom list in config to grant access.",
-                sender_id, self.name,
+                sender_id,
             )
             return