Remove redundant migration name overrides and simplify registry to class

[tudddorrr]

Migration cleanup

• Dropped the redundant override name from AddOrganisationAndUserDeletedAtColumns, AddPlayersToDeleteUniqueConstraint, and CreateEventFunnelsTable, since the class name already matches.

Registry simplification

• Rewrote src/migrations/index.ts to export migration classes directly instead of { name, class } object entries, cutting out ~250 lines of duplicated names.

Why it matters

• The registry no longer risks name drift from the class declaration, and future migrations get a shorter additions checklist.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.42%. Comparing base (2452274) to head (7b0ad60).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #1047   +/-   ##
========================================
  Coverage    98.42%   98.42%           
========================================
  Files          477      477           
  Lines         7613     7613           
  Branches       999      999           
========================================
  Hits          7493     7493           
  Misses          49       49           
  Partials        71       71           

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