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.

Docs/Tasks.md

@@ -44,6 +44,8 @@ Reference: `Docs/Refactoring.md` for full analysis of each issue.
 
 **Why this is needed:** Routers should not reach into service internals to import exception types. All domain exceptions belong in the central registry so `main.py` global handlers and any future middleware can catch them uniformly.
 
+**Status:** Completed ✅
+
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 ### Task 3 — Eliminate the `config_file_service.py` delegation façade