fix(compose): widen mobile recipient selection

[keilogic]

Summary

• Closes Make email selection field wider on small screens #300 by giving the compose recipient input a viewport-aware autocomplete panel width on small screens.
• Moves recipient input sizing out of inline styles into a component stylesheet.
• Lets long recipient chips and autocomplete options wrap instead of clipping when the address spans multiple lines.
• Adds focused component coverage for the mobile autocomplete panel width and responsive recipient chip/input markup.

Validation

• Red baseline before the implementation commit: npx ng test runbox7 --watch=false --include=src/app/compose/mailrecipientinput.component.spec.ts failed with TOTAL: 2 FAILED, 0 SUCCESS because the autocomplete panel width and responsive chip/input classes did not exist.
• npx ng test runbox7 --watch=false --include=src/app/compose/mailrecipientinput.component.spec.ts (passes, TOTAL: 2 SUCCESS)
• npx tsc -p src/tsconfig.app.json --noEmit
• npx tsc -p src/tsconfig.spec.json --noEmit
• npm run lint -- --quiet
• npm run policy (passes; output still includes existing historical commit-message warnings)
• git diff --check origin/master...HEAD
• git show --check --stat --oneline HEAD
• $env:SKIP_CHANGELOG='1'; node src/build/pre-build.js; npx ng build --configuration production --base-href=/app/ runbox7; node src/build/post-build.js (passes with existing warnings, build hash 92555d3199549f66)

AI disclosure

This PR was prepared with OpenAI Codex assistance. I used Codex to inspect the issue and current recipient input implementation, draft the focused component spec and responsive styling changes, and run the validation commands listed above.