…lize field/control sizing

Filter tags by the owning user so accounts no longer see each other's tags,
and surface them in guest mode from the populated objects. Add a Create
Library button on the home page and disable both it and the dropdown's My
Library entry when the user can neither create nor already owns a library.
Route library cards by id to sidestep the username->id filter the API
currently 500s on. Standardize library inputs, buttons, date picker, and
dropdown to a 44px height with 16px input text, plus assorted toolbar,
overview, and step-indicator polish.

Co-Authored-By: Claude Opus 4.7 <[email protected]>