chore: format the tree and clear ruff's findings

Applies ruff format, ruff check --fix and prettier, so CI can gate on all three.
The surviving unused imports were all re-exports in __init__.py, now covered by a
per-file ignore; the pdf.js viewer and the generated openapi types join the
vendored code that eslint and prettier already skip.

frontend/src/lib/components/layout/app-sidebar.svelte

@@ -28,7 +28,9 @@
 	// directly in the markup keeps it static.
 	const header = $derived({
 		title: 'chitai',
-		url: resolve('/(root)/(library)/library/[libraryId]', { libraryId: String(libraryState.activeLibrary!.id) })
+		url: resolve('/(root)/(library)/library/[libraryId]', {
+			libraryId: String(libraryState.activeLibrary!.id)
+		})
 	});
 </script>