feat(backend): add deprecation middleware and API versioning support

- Add deprecation middleware for warning headers on sunset endpoints
- Add jails_v2 router for API v2 migration path
- Update CI workflow with new test coverage
- Update API versioning documentation
- Remove completed tasks from Tasks.md

Docs/Tasks.md

@@ -1,30 +1,3 @@
-### Issue #55: MEDIUM - Correlation ID Scope Is Module-Level (Resets on HMR)
-
-**Where found**:
-- `frontend/src/api/client.ts:26-39` – `sessionCorrelationId` stored as a module variable
-
-**Why this is needed**:
-Hot Module Replacement (HMR) re-evaluates modules, generating a new correlation ID mid-session. Distributed traces lose continuity, making it impossible to correlate logs from the same user session.
-
-**Goal**:
-Persist the correlation ID across module re-evaluations for the lifetime of the browser tab.
-
-**What to do**:
-1. Store the correlation ID in `sessionStorage` on first generation; read from there on subsequent module evaluations.
-2. Clear it on logout.
-
-**Possible traps and issues**:
-- `sessionStorage` is tab-local, which is the desired scope.
-- Ensure the ID is not leaked in URLs or logs.
-
-**Docs changes needed**:
-- Add comment explaining the persistence strategy in `client.ts`.
-
-**Doc references**:
-- `frontend/src/api/client.ts` – `getSessionCorrelationId()`
-
----
-
 ### Issue #56: MEDIUM - No API Versioning or Deprecation Strategy
 
 **Where found**: