feat: add browser remote text size setting

[nathanael]

Summary

• Adds a configurable text size setting (SM/MD/LG/XL) for the browser remote viewer
• New BrowserFontSizePreset enum with responsive CSS clamp formulas for desktop and mobile
• Segmented picker in Settings > Remote tab, visible when remote connection is enabled
• Default is LG, which closely matches the previous hardcoded sizing

Test plan

• Open Settings > Remote, enable Remote Connection — "Remote Text Size" picker appears with SM/MD/LG/XL
• Default selection is LG
• Open browser remote URL, confirm text displays at expected size
• Change preset, refresh browser — text size changes accordingly
• Cycle through all four presets to verify scaling from smallest (SM) to largest (XL)
• Test mobile breakpoint (browser dev tools, width < 768px)
• Reset to Defaults resets text size back to LG

🤖 Generated with Claude Code

[skobylite]

Alternative approach to consider (no pressure to pivot from this PR):
I put together an on-device version while working on the remote view. It uses a quick-tap pill to cycle XS → XL, persists via localStorage, and supports a ?size=L query param.

my reasoning:

• Ergonomics: If the phone is rigged up and the Mac is behind the camera, you can adjust size right on the screen you're reading from without walking over to reload.
• Per-device state: An iPad and a phone aren't locked to the same scale.
• Footprint: ~40 LOC since it skips the enum and Settings UI.

Yours is definitely more discoverable within standard app settings, so up to you. I can open a PR, fold it in here (or not)