Mark Task 20 complete and document global exception handlers

Docs/Refactoring.md

@@ -8,5 +8,6 @@ This document catalogues architecture violations, code smells, and structural is
 
 - Moved `Fail2BanConnectionError` and `Fail2BanProtocolError` from `backend/app/utils/fail2ban_client.py` into `backend/app/exceptions.py`. Updated all router, service, and test call sites to import these domain exceptions from `app.exceptions` and retained backward compatibility through re-exporting in `app.utils.fail2ban_client`.
 - Moved config file exceptions (`ConfigDirError`, `ConfigFileNotFoundError`, `ConfigFileExistsError`, `ConfigFileWriteError`, `ConfigFileNameError`) from `backend/app/services/raw_config_io_service.py` into `backend/app/exceptions.py`. Updated router and tests to import the shared domain exceptions from `app.exceptions`.
+- Added global domain exception handlers to `backend/app/main.py` so domain exceptions like `JailNotFoundError`, `ConfigValidationError`, and `ConfigWriteError` map consistently to 404, 400, and 500 responses.
 - Fixed stale activation tracking in `backend/app/routers/jail_config.py` by recording `last_activation` only after a successful jail activation and preventing a failed activation attempt from leaving a stale runtime state record.
 

Docs/Tasks.md

@@ -348,6 +348,8 @@ Reference: `Docs/Refactoring.md` for full analysis of each issue.
 
 **Docs changes needed:** None.
 
+**Status:** Completed ✅
+
 **Why this is needed:** `__import__()` is an implementation detail of Python's import system and should never appear in application code. It obscures the dependency, bypasses linting checks, and signals that the code was written reactively to solve a circular import that no longer exists.
 
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@@ -385,6 +387,8 @@ Reference: `Docs/Refactoring.md` for full analysis of each issue.
 
 **Docs changes needed:** Update `Docs/Refactoring.md`.
 
+**Status:** Completed ✅
+
 **Why this is needed:** The same try/except→HTTPException conversion is duplicated across every router endpoint. Global handlers reduce boilerplate, make error mapping auditable in one place, and prevent inconsistencies where the same exception produces different status codes in different routes.
 
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