Remove deprecated "submission" ScheduleItem type

[marcoacierno]

What

submission is no longer used and has been replaced with talk, tutorial, panel etc.

The FE used this talks query that didn't work while the detail itself worked as it used talk (which queries all schedule items). We likely don't need to pre-render the event pages every deploy and can rely on the node server rendering them on demand like it is doing right now anyway

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
pycon	Ready	Preview	Aug 16, 2026 12:07pm

[claude]

Removes the deprecated submission ScheduleItem type (already data-migrated to talk back in migration 0041), updates callers/tests accordingly, and adds the corresponding schema migration.

• backend/importer/management/commands/import_old_db.py:503 still creates ScheduleItem rows with type="submission" if submission else "custom". Since submission is no longer a valid TYPES choice after this change, this legacy importer needs updating to use "talk" instead, otherwise it will keep writing an invalid/unrecognized type value that won't match the talk/training filters used elsewhere (e.g. schedule/admin.py, conferences/admin/conference.py).
• conferences/types.py's talks field now unconditionally returns self.schedule_items.none(). This matches the field's actual behavior since 2022 (no data has had type=submission since migration 0041), but it's worth confirming this is intentional to keep as permanently dead code (it backs the frontend's AllTalks/getStaticPaths query in frontend/src/pages/event/[slug]/index.tsx, which will keep pre-building zero static talk paths) rather than switching the filter to type=talk to restore the original intent of listing talks.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.11%. Comparing base (29e4c07) to head (bcb0a57).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4805      +/-   ##
==========================================
- Coverage   93.11%   93.11%   -0.01%     
==========================================
  Files         360      360              
  Lines       11239    11236       -3     
  Branches      905      904       -1     
==========================================
- Hits        10465    10462       -3     
  Misses        663      663              
  Partials      111      111              

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.