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/routes/(root)/settings/devices/+page.svelte

@@ -109,9 +109,7 @@
 				<Smartphone />
 			</Empty.Media>
 			<Empty.Title>No devices</Empty.Title>
-			<Empty.Description>
-				Add a device to sync your KOReader reading progress.
-			</Empty.Description>
+			<Empty.Description>Add a device to sync your KOReader reading progress.</Empty.Description>
 		</Empty.Header>
 		<Empty.Content>
 			<Button onclick={() => (createDialogOpen = true)}>
@@ -224,12 +222,14 @@
 		<AlertDialog.Header>
 			<AlertDialog.Title>Regenerate API key?</AlertDialog.Title>
 			<AlertDialog.Description>
-				This will invalidate the current API key for "{regenerateConfirmDevice?.name}".
-				You will need to update the key in your KOReader device settings.
+				This will invalidate the current API key for "{regenerateConfirmDevice?.name}". You will
+				need to update the key in your KOReader device settings.
 			</AlertDialog.Description>
 		</AlertDialog.Header>
 		<AlertDialog.Footer>
-			<AlertDialog.Cancel onclick={() => (regenerateConfirmDevice = null)}>Cancel</AlertDialog.Cancel>
+			<AlertDialog.Cancel onclick={() => (regenerateConfirmDevice = null)}
+				>Cancel</AlertDialog.Cancel
+			>
 			<AlertDialog.Action
 				onclick={() => regenerateConfirmDevice && handleRegenerate(regenerateConfirmDevice)}
 			>