Add Duration Range Filter to Finished Games Search

[MichaelDeitz]

The backend now supports filtering finished matches by minimum and maximum duration (in seconds).
The website UI should expose this filter so users can search for games within a specific duration range.

Backend Work (already completed)
New Query Parameters
The /api/matches endpoint now accepts:

• minDuration — minimum match duration in seconds
• maxDuration — maximum match duration in seconds

Model Field Used
The backend filters on:
Matchup.Duration (TimeSpan)
which maps to the stored durationInSeconds field in MongoDB

Here is where it is expected to be.

Frontend Work Needed
Add two numeric inputs for:

• Min Duration (seconds)
• Max Duration (seconds)
  These should be placed in the Matches filter panel, in the same section as the MMR range filters (see screenshot).
  When values are entered, the frontend should append them to the API request:
  minDuration=
  maxDuration=