Study card: label the answer and "key takeaway" as distinct sections
with a real visible divider (previously an all-but-invisible
HSeparator) instead of one undifferentiated block of text. Also fixes
a real gap where a cloze card's extra field was silently dropped,
since only basic notes combined answer+extra into one label. Bigger
card, gradient Show-Answer button matching the app's signature CTA
style instead of a duller flat teal, and the Undo button now hides
itself when there's nothing to undo instead of sitting there disabled
looking identical to a real action.
Library: colored type badge per card (Basic/Cloze) instead of plain
gray text, more breathing room inside each row, Study promoted to the
same gradient CTA style, and Edit/Archive given a real secondary
button treatment instead of default theme buttons. Note editor fields
renamed ("Back / Extra takeaway" + a separate "Extra" field was
genuinely confusing) and now show which deck a card is being saved to.
Import and export were stubbed with status-text placeholders; wire them
to the existing backend endpoints with a real file picker (web JS
bridge or native FileDialog) and browser/desktop download, plus an
import preview with create/update/skip/error counts before commit.
Also fix the library and study screens' theme-refresh handlers, which
were no-op stubs so cards never restyled on a theme toggle, and add
responsive layout handling for narrow viewports.
Adds a full flashcards system: FSRS-based scheduling, cloze/basic
card types, CSV import/export, media storage, and study UI, wired
into navigation and the dashboard alongside existing question flows.