feat: Implement Event File Hosted Data Fix and API Guide Update

Address critical data visibility issues for Event Files and enhance frontend documentation.

This commit resolves the persistent problem where top-level hosted file convenience fields
(e.g., , , ) were
returning as  in V3 Event File API responses, even when .

Key changes include:
- Refactored  Pydantic model:
    - Removed redundant  definitions from top-level hosted file convenience fields,
      allowing direct mapping from SQL view columns.
    - Simplified  to focus solely on conditionally loading the nested
       object, as top-level fields are now populated directly by Pydantic
      from the  view.
    - Added comprehensive comments to clarify data flow, Pydantic's behavior, and the
      expected origin of these convenience fields from SQL views.
- Updated :
    - Introduced a new section detailing how to retrieve Event File data, including the
      use of  to get both top-level convenience fields and a nested
       object.
    - Clarified all ID references as random string IDs.
    - Renumbered the troubleshooting section.
- Copied updated guide to .
- Continued ID Vision compliance audit, ensuring consistent handling of random string IDs
  across various core and event models (Account, Address, Contact, DataStore, Event Badge Template).
- Consolidated ID Vision E2E tests and updated related documentation.
- Minor updates to  and
  to support Event File data retrieval with .

tests/README.md

@@ -24,6 +24,7 @@ These consolidated scripts are the primary verification tool for the V3 API.
 | `test_e2e_redis_extensive.py` | **Redis Stress**: Benchmarks bidirectional ID caching across thousands of records. |
 | `test_e2e_v3_event_vision_parity.py`| **Vision ID**: Verifies string-ID enforcement across event models. |
 | `test_e2e_v3_cms_vision_parity.py`| **Vision ID**: Verifies string-ID enforcement across CMS (post/comment) models. |
+| `test_e2e_v3_core_vision_parity.py`| **Vision ID**: Verifies string-ID and polymorphic resolution across core models (Account, Person, Address, Contact, DataStore). |
 | `test_e2e_v3_demo_parity.py` | **Demo Parity**: Comprehensive check for Badge, Exhibit, Tracking, and nested Journal Entries. |
 | `test_e2e_v3_action_event_file.py` | **Event Actions**: Specialized atomic upload and linking for event files. |
 | `test_e2e_v3_action_zoom.py` | **Zoom Integration**: Verifies OAuth and ticket sync logic for Zoom Events. |