docs: add database context manager to completed work

ROADMAP.md

@@ -348,6 +348,12 @@ PPF (Proxy Fetcher) is a Python 2 proxy scraping and validation framework design
 - [x] Thread-safe with lock for concurrent access
 - [x] Proper LRU eviction (move_to_end on hits, popitem oldest when full)
 
+### Database Context Manager (Done)
+- [x] Refactored all DB operations to use `_db_context()` context manager
+- [x] Connections guaranteed to close even on exceptions
+- [x] Removed deprecated `_prep_db()` and `_close_db()` methods
+- [x] `fetch_rows()` now accepts db parameter for cleaner dependency injection
+
 ---
 
 ## Technical Debt