Updated the EPG generation logic to ensure that channels without a channel number do not cause crashes in the XMLTV export. Implemented a deferred assignment mechanism for channels with null numbers, allowing them to receive valid integers during processing. Added tests to verify that the XMLTV output remains stable and valid even when channels are unnumbered.
- Moved the `programme_index` from the `EPGSource` model to a new `EPGSourceIndex` table, ensuring that the large JSON blob is only loaded when explicitly accessed, thus improving query performance and memory efficiency.
- Updated related queries and API views to utilize the new structure, including adjustments to EPG generation and import logic to prevent unnecessary data loading.
- Enhanced memory management in the EPG grid endpoint to reduce worker RSS during response handling.
- Moved all XMLTV output logic from `apps/output/views.py` to `apps/output/epg.py`, streamlining the codebase and maintaining the existing HTTP endpoint functionality.
- Updated related tests and references to ensure proper integration with the new module structure.
