Fix web responsiveness on mobile and small desktop screens

[editinghero]

Added CSS media queries to web/src/style.css to fix the layout on mobile and small desktop screens. This includes wrapping the top bar, setting the search bar to full width, simplifying action buttons to hide text labels and new-note buttons, forcing the notes grid to a single column, and properly managing the visibility of the mobile bottom dock.

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PR created automatically by Jules for task 6927376651190306239 started by @editinghero

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[editinghero]

Merged locally into main in commit aa1eaae with additional security hardening and biometric cleanup.