chore(api): stabilize SQL core and enhance searchability

- Refactor SQL CRUD to use engine.connect() context managers for thread safety
- Optimize connection pooling in lib_sql_core
- Clean up app/routers/api.py to fix duplicate definitions and OpenAPI KeyError
- Add 'default_qry_str' to searchable_fields for Event, Session, Presentation, Presenter, Badge, and Journal
- Add 'event_location_name' to searchable_fields for Event Session
- Verified 20/20 E2E success via repro_intermittent_errors.py

app/object_definitions/journals.py

@@ -24,7 +24,7 @@ journal_obj_li = {
             'journal_id_random', 'account_id_random', 'person_id_random', 'user_id_random',
             'name', 'short_name', 'summary', 'outline',
             'description', 'type_code', 'tags', 'billable', 'enable', 'hide',
-            'priority', 'sort', 'group', 'notes', 'created_on', 'updated_on'
+            'priority', 'sort', 'group', 'notes', 'created_on', 'updated_on', 'default_qry_str'
         ],
     },
     'journal_entry': {