chore(format): run prettier over src/ and scripts/

Formatting was configured but never enforced: `bun run format:check`
reported 199 unformatted files and ran in no workflow and in no git hook,
so .prettierrc (printWidth 100, trailing commas) described an intention
rather than the tree.

This is the one-time sweep that makes the check gateable. Whitespace and
token-reflow only -- no behavioural change: `bun run check` reports 0
errors and all 1053 frontend tests pass before and after.

Kept out of every other commit on purpose. A 199-file diff mixed with
real changes is unreviewable, and the next commit turns format:check
into a hard CI gate so this cannot silently accumulate again.

src/lib/components/library/libraryMosaic.test.ts

@@ -42,7 +42,11 @@ describe("buildLibraryMosaic", () => {
   it("links a category tile to that category's favourites tab", () => {
     const entries = buildLibraryMosaic([SHOWS]);
     const tile = entries.find((e) => e.label === "Favourite Shows");
-    expect(tile).toMatchObject({ kind: "favorites", scope: "tv", href: "/library/favorites?scope=tv" });
+    expect(tile).toMatchObject({
+      kind: "favorites",
+      scope: "tv",
+      href: "/library/favorites?scope=tv",
+    });
   });
 
   it("offers a category's favourites once, however many libraries share it", () => {