fix(stats): refresh Overview data after deleting sessions

- Add a refresh key to OverviewTab that refetches overview, streak calendar, and known-words summary after single, day, or anime session deletes
- Reset loading/error state in useStreakCalendar on refetch
- Add OverviewTab tests covering each delete mode and a failed delete
- Document the automatic refresh and add changelog fragments

changes/stats-mining-and-delete-accuracy.md

@@ -4,3 +4,4 @@ area: stats
 - Fixed sentence mining (single and multi-line) counting each created card twice in session and lifetime stats.
 - Fixed deleting a session leaving word and kanji "last seen" dates pointing at the deleted session; affected rows are repaired once in the background on next launch.
 - Fixed re-seen words that the vocabulary filter hides still being counted in the new-words charts, so charts and the vocabulary summary now agree. Existing mismatches are repaired by the same background pass.
+- Fixed Overview totals, charts, activity calendar, and vocabulary summary staying stale after deleting sessions.

changes/stats-overview-refresh-docs.md

@@ -0,0 +1,4 @@
+type: docs
+area: stats
+
+- Documented the automatic Overview refresh after deleting sessions or session groups.