fix(files): a steady list header, every user on the Storage tab, the name gets the row's room

- The Files list starts at the scroller's top: the padding above it let the sticky header ride up
  12px on the first scroll, then stop.
- Users -> Storage lists every user with their quota, not only those already holding a file — a
  quota is set before anyone downloads.
- On a wide Files list only the "…" holds a place; Copy link, Share and Save come up over the date
  while the row is hovered or holds the keyboard (a card keeps them in its line). Keeps is narrower.

frontend/src/components/Files.menu.dom.test.tsx

@@ -1,7 +1,8 @@
 // @vitest-environment jsdom
 //
-// The Files page: a row keeps Copy link, Share, Save and its "…" in sight — a slot an action does not
-// apply to stays empty, so the icons line up down the list — and its every action is its ONE menu,
+// The Files page: a row has Copy link, Share and Save (on a wide list, shown while it is hovered or
+// focused) and its "…" — a slot an action does not apply to stays empty, so the icons line up down
+// the list — and its every action is its ONE menu,
 // opened by the "…" or a right-click. Renaming happens in the row; moving goes to an own folder or
 // back home; a shared file is the owner's, so its menu only plays, saves, cuts or drops it from my
 // list. i18n is key-passthrough, so labels read as keys.
@@ -177,6 +178,20 @@ describe("Files · my file's row", () => {
     ]);
   });
 
+  it("holds back the quick icons on a wide row until it is hovered or focused; the '…' stays", () => {
+    mocks.files = [file(2)];
+    mocks.folders = [YT];
+    mount();
+    const row = rowOf("Clip 2");
+    const quick = row.querySelector<HTMLElement>("[data-quick-actions]")!;
+    expect(row.className).toMatch(/(^|\s)group(\s|$)/);
+    expect(quick.className).toContain("md:opacity-0");
+    expect(quick.className).toContain("md:group-hover:opacity-100");
+    expect(quick.className).toContain("md:group-focus-within:opacity-100");
+    expect(quick.contains(row.querySelector('[aria-label="files.actions.share"]'))).toBe(true);
+    expect(quick.contains(moreOf("Clip 2"))).toBe(false);
+  });
+
   it("keeps the slot of an action a plain file lacks, so the icons line up", () => {
     mocks.files = [file(3, { job_kind: "upload", asset: { media_kind: "file" } } as never)];
     mocks.folders = [YT];
@@ -388,6 +403,14 @@ describe("Files · a shared file's row", () => {
 });
 
 describe("Files · the view", () => {
+  it("starts the list at the scroller's top, so its sticky header does not jump on the first scroll", () => {
+    mocks.files = [file(2)];
+    mocks.folders = [YT];
+    mount();
+    const list = screen.getByRole("table").closest<HTMLElement>(".max-w-7xl")!;
+    expect(list.className).not.toMatch(/(^|\s)(pt|py|p)-/);
+  });
+
   it("reads one folder's files and names the folder", () => {
     mocks.files = [file(2, { folder_id: 2 })];
     mocks.folders = [YT, OWN];