Put the interface into English, and give the notebook one way in

The interface had drifted into two languages — the frame in English, everything
added later in German — which is worse than either, since the same idea appeared
under two names depending on when that part was written. Sorting by title still
uses the German collation, so Übung 2 comes before Übung 10: that is about the
notes, not the chrome.

Two archive folders were renamed with it (bilder/ → images/, zeichnungen/ →
drawings/). The importer reads both spellings, and both the old and new marker
line for a drawing — archives exported before this are on disk, and an import
that quietly dropped their drawings would be the worst kind of tidy-up.

Making a note, uploading a PDF and importing Markdown were three buttons side by
side, two of them icons you had to hover to identify. They are the same act —
putting something new in this notebook — so they are now one + menu.

The search box moves out of the sidebar and into the note list, labelled with the
notebook it narrows. Nothing changed about what it does: it has always searched
only the notebook you are in, but from the sidebar it read as searching
everything.

A separator no longer carries a sentence explaining the order the sort menu
already names. Renaming joins removing on the right-click menu — a left-click on
the label started an edit, so the row could not be touched without falling into
one.

218 unit tests, 238 browser checks across eleven suites. Two of those caught real
breakage from this change rather than needing a translation.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

e2e/editor.mjs

@@ -49,18 +49,18 @@ try {
   const before = await cellCount();
   await p.locator(".ProseMirror table td").first().click({ button: "right" });
   await p.waitForTimeout(600);
-  check((await p.getByText("Zeile darunter einfügen").count()) > 0, "right-click in a table opens the table menu");
-  check((await p.getByText("Tabelle löschen").count()) > 0, "and offers deleting the table");
+  check((await p.getByText("Insert row below").count()) > 0, "right-click in a table opens the table menu");
+  check((await p.getByText("Delete table").count()) > 0, "and offers deleting the table");
   await p.screenshot({ path: `${OUT}/editor-table-menu.png` });
 
-  await p.getByText("Zeile darunter einfügen").click();
+  await p.getByText("Insert row below").click();
   await p.waitForTimeout(1000);
   check((await cellCount()) > before, "the menu really added a row", `${before} → ${await cellCount()}`);
 
   const withRow = await cellCount();
   await p.locator(".ProseMirror table td").first().click({ button: "right" });
   await p.waitForTimeout(600);
-  await p.getByText("Zeile löschen").click();
+  await p.getByText("Delete row").click();
   await p.waitForTimeout(1000);
   check((await cellCount()) < withRow, "and removing one works too", `${withRow} → ${await cellCount()}`);
 
@@ -68,7 +68,7 @@ try {
   await p.locator(".ProseMirror p").first().click({ button: "right" });
   await p.waitForTimeout(500);
   check(
-    (await p.getByText("Zeile darunter einfügen").count()) === 0,
+    (await p.getByText("Insert row below").count()) === 0,
     "right-click outside a table shows no table menu"
   );
   await p.keyboard.press("Escape");