feat: modality-based URLs (/image/resize, /video/compress-video)

Tool routes now include the modality prefix: /image/crop, /video/trim-video,
/audio/convert-audio, /document/merge-pdf, /data/csv-json. Old URLs
(e.g. /resize) redirect to the new modality-prefixed path automatically.

Routes are computed by prepending MODALITY_URL_SLUG to each tool's route
in the TOOLS array at module init. The App.tsx route changed from
/:toolId to /:modality/:toolId, with a LegacyToolRedirect fallback.

packages/shared/src/modality.ts

@@ -119,6 +119,14 @@ export const DOCUMENT_INPUTS = [
 ];
 export const FILE_INPUTS = [".csv", ".json", ".xml", ".yaml", ".yml", ".zip"];
 
+export const MODALITY_URL_SLUG: Record<Modality, string> = {
+  image: "image",
+  video: "video",
+  audio: "audio",
+  document: "document",
+  file: "data",
+};
+
 export function detectModalityFromMime(mime: string): Modality {
   if (mime.startsWith("image/")) return "image";
   if (mime.startsWith("video/")) return "video";