Add admin stats delete route

[tudddorrr]

Admin API for game stat deletion

• Added a new DELETE endpoint at /admin/v1/game-stats/:id allowing admin API keys to delete game stats, gated by the WRITE_STATS scope.

Shared deletion logic

• Extracted the stat deletion handler from the protected route into a reusable deleteStatHandler function that accepts either a User or AdminAPIKey as the actor, enabling both the protected and admin routes to share the same business logic (activity logging, entity removal, cache invalidation).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.35%. Comparing base (3a1e89f) to head (d480839).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1021      +/-   ##
===========================================
+ Coverage    98.33%   98.35%   +0.01%     
===========================================
  Files          443      444       +1     
  Lines         7274     7276       +2     
  Branches       976      976              
===========================================
+ Hits          7153     7156       +3     
  Misses          49       49              
+ Partials        72       71       -1     

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