Fix follower tab counts, achievement styling, and link URLs

[dmetzner]

Summary

• Fix follower page tab counts showing "-" instead of numbers (added count_id support to TabBar component)
• Fix achievement badge SVGs rendering at massive sizes (pre-set width/height on SVG placeholders to block external-svg-loader from copying pt-based dimensions)
• Fix follower page profile links missing theme prefix (e.g. /user/123 instead of /app/user/123) causing 404s
• Fix profile page achievements not loading for guest users (ApiFetch always sends auth header, replaced with plain fetch for public endpoint)
• Move most-recent-achievement section above tabs to match original layout
• Constrain follower card avatar images to 4rem

Test plan

• Verify follower page (/app/follower) shows correct numeric counts in tabs
• Verify follower page links to user profiles work (include theme prefix)
• Verify achievement badges render at correct size on /app/achievements
• Verify achievement badges render at correct size on /app/user/{id} profile pages
• Verify achievements show on profile pages when not logged in
• Verify most-recent-achievement section appears above the tab bar
• Run bin/behat -s web-profile tests/BehatFeatures/web/profile/follow.feature — all 10 scenarios pass

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 52.85%. Comparing base (544e477) to head (2403e60).
⚠️ Report is 15 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop    #6252      +/-   ##
=============================================
- Coverage      54.58%   52.85%   -1.73%     
  Complexity      8369     8369              
=============================================
  Files            756      756              
  Lines          26801    26801              
=============================================
- Hits           14629    14167     -462     
- Misses         12172    12634     +462     

Flag	Coverage Δ
behat	50.34% <ø> (-1.91%)	⬇️
phpunit	10.81% <ø> (ø)

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