enh(a11y): Add search contacts label

[Pytal]

• For [BITV] 9.3.3.2/2.3 - Header / menus "Search" and "Search contacts" - Search input fields lack visual labels and there are no search buttons or symbols to help identify them as search fields. (9) #37085

Summary

Before	After

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)