Move config file exceptions into app.exceptions

Move ConfigDirError, ConfigFileNotFoundError, ConfigFileExistsError, ConfigFileWriteError, and ConfigFileNameError from raw_config_io_service into the shared domain exception module. Update router and tests to import the exceptions from app.exceptions.

backend/app/exceptions.py

@@ -23,6 +23,44 @@ class ConfigOperationError(Exception):
     """Raised when a config payload update or command fails."""
 
 
+class ConfigDirError(Exception):
+    """Raised when the fail2ban config directory is missing or inaccessible."""
+
+
+class ConfigFileNotFoundError(Exception):
+    """Raised when a requested config file does not exist."""
+
+    def __init__(self, filename: str) -> None:
+        """Initialize with the filename that was not found.
+
+        Args:
+            filename: The filename that could not be located.
+        """
+        self.filename = filename
+        super().__init__(f"Config file not found: {filename!r}")
+
+
+class ConfigFileExistsError(Exception):
+    """Raised when trying to create a file that already exists."""
+
+    def __init__(self, filename: str) -> None:
+        """Initialize with the filename that already exists.
+
+        Args:
+            filename: The filename that conflicts.
+        """
+        self.filename = filename
+        super().__init__(f"Config file already exists: {filename!r}")
+
+
+class ConfigFileWriteError(Exception):
+    """Raised when a file cannot be written (permissions, disk full, etc.)."""
+
+
+class ConfigFileNameError(Exception):
+    """Raised when a supplied filename is invalid or unsafe."""
+
+
 class ServerOperationError(Exception):
     """Raised when a server control command (e.g. refresh) fails."""