[release] Start Development 2026.1.0

[cbentejac]

Following the release of Meshroom 2025.1.0, this PR sets the current version to 2026.1.0 with the "develop" status.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.46%. Comparing base (a576d81) to head (e2b9e87).
⚠️ Report is 3 commits behind head on develop.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2840      +/-   ##
===========================================
+ Coverage    77.31%   77.46%   +0.14%     
===========================================
  Files           48       48              
  Lines         6735     6735              
===========================================
+ Hits          5207     5217      +10     
+ Misses        1528     1518      -10     

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