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/ui/popover/popover.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-	import { Popover as PopoverPrimitive } from "bits-ui";
+	import { Popover as PopoverPrimitive } from 'bits-ui';
 
 	let { open = $bindable(false), ...restProps }: PopoverPrimitive.RootProps = $props();
 </script>