Add TCG Strat to MTGJSON Powered Applications

[ZeldaZach]

Adds TCG Strat to the MTGJSON Powered Applications list, requested in #718.

• New entry in docs/.vitepress/theme/static/applications.json, placed alphabetically after TCGplayer.
• New avatar docs/public/images/avatars/avatar-tcgstrat.svg, taken from the site's favicon. The original SVG swapped its fill to white under prefers-color-scheme: dark; since .img-wrap is always white, the fill is hardcoded to #000 so the mark stays visible for readers on either system theme.

Closes #718

🤖 Generated with Claude Code

https://claude.ai/code/session_0167TPijiNcVNU8V566N7zjd

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (cd004fd) to head (9c890bc).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #728   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            1         1           
  Lines           69        69           
  Branches        27        27           
=========================================
  Hits            69        69           

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