feat: sharing tests, property tests, tag-share UI, inline errors, route fix

- Add 10 sharing endpoint tests (share/unshare memory, tag shares, shared-with-me,
  my-shares, recall with shared, update permission checks)
- Add hypothesis property-based tests for model validation (roundtrip, bounds,
  enum, sort_by, limit)
- Tighten model validation: sort_by Literal, limit ge=1/le=500, tags/keywords max_length
- Fix dashboard shared_with_me stat to include tag-based shares
- Add tag-sharing management UI (share/remove tags, user typeahead)
- Replace alert() with inline error messages
- Fix route ordering bug: share-tag routes before {memory_id} parameterized routes

.gitignore

@@ -43,3 +43,4 @@ docker/pgdata/
 # Database
 *.db
 *.sqlite3
+.hypothesis/