Normalize desktop icon sizing

[klopez4212]

Summary

• normalize standard desktop icon glyphs to 16px across shared buttons and UI surfaces
• update remaining channel member, huddle, settings, profile, message, and reminder icon callsites that were still 14px/18px/20px
• leave non-standard avatars, status dots, skeletons, media illustrations, and decorative state artwork unchanged

Validation

• git diff --check
• cd desktop && ./node_modules/.bin/tsc --noEmit
• cd desktop && ../node_modules/.bin/biome check <changed files>
• cd desktop && node scripts/check-px-text.mjs
• cd desktop && node scripts/check-file-sizes.mjs
• targeted scan for lingering 18px / size-4.5 icon sizing
• cd desktop && ./node_modules/.bin/vite build

Screenshot

Posted separately as a PR comment.

[klopez4212]

🤖 Refreshed channel-page screenshot for #1088 (Normalize desktop icon sizing).

The previous image was captured from stale desktop/dist output that still contained [&_svg]:size-4.5. After a clean rebuild, the channel header Users, Headphones, and settings icons measure 16px in Chromium.

Code checks/builds run:

• git diff --check
• cd desktop && ./node_modules/.bin/tsc --noEmit
• cd desktop && ../node_modules/.bin/biome check <changed files>
• cd desktop && node scripts/check-px-text.mjs
• cd desktop && node scripts/check-file-sizes.mjs
• targeted scan for lingering 18px / size-4.5 icon sizing
• cd desktop && ./node_modules/.bin/vite build
• clean rebuild after removing stale desktop/dist

Channel page icon sizing