Fellowship updates

[jhdark]

Description

Summary

Adds a proper Fellows page now that we have three Fellows in the Summer 2026 cohort, and tidies up the fellowship section while I was in there.

• New docs/source/fellowship/fellows.rst with profiles + project titles for Arpan Sircar (ORNL), Ian Wojtowicz (UMN) and Emre Yildirim (Type One Energy), plus the Previous Fellows section moved over from the main fellowship page.
• Moved fellowship_tez.rst into the new fellowship/ subfolder so all the fellowship pages live together, and added a hidden toctree on fellowship.rst so both pages are reachable.
• fellowship.rst now links out to the Fellows page via a "Meet the FESTIM Fellows" card instead of embedding Tez's card directly, with a short line on the current cohort.
• Filled in the actual dates for the Fall cohort timeline (was just month names).
• Added profile photos and a small CSS rule — the global h3 hotfix made the fellow names too small to read as names, so they're bumped back up on that page only.

Related Issues

Motivation and Context

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 🔨 Code refactoring (no functional changes, no API changes)
• 📝 Documentation update
• ✅ Test update (adding missing tests or correcting existing tests)
• 🔧 Build/CI configuration change

Testing

• All existing tests pass locally (pytest)
• I have added new tests that prove my fix is effective or that my feature works

Code Quality Checklist

• My code follows the code style of this project (Ruff formatted: ruff format .)
• My code passes linting checks (ruff check .)
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas

Documentation

• I have updated the documentation accordingly (if applicable)
• I have added docstrings to new functions/classes following the project conventions

Breaking Changes

Screenshots/Examples

Additional Notes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.19%. Comparing base (ac4b4f5) to head (a4c54bf).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1189   +/-   ##
=======================================
  Coverage   95.19%   95.19%           
=======================================
  Files          53       53           
  Lines        3952     3952           
=======================================
  Hits         3762     3762           
  Misses        190      190           

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