Move fastext nav to page top, fix Settings header, add working search

- Fastext colour keys now lead every page but the index, since they're
  the only nav those pages carry; the index keeps them as its closing
  row since its own body is already the full nav.
- Settings page was missing page="settings" in its render_template
  call, so its header silently fell back to "P100 Index".
- Library's search form posted a q param the route never read; it now
  filters the cached Sonarr/Radarr lists and shows matching tiles.
- Discover gained a search bar that queries Ombi (already in front of
  TMDB/TVDB) and lets you add a result straight to Radarr/Sonarr,
  showing "Held" instead of a button for anything already in library.
- Fixed the Add button's success check, which read d.ok against a
  response that actually sets d.success — it reported FAILED even
  when the add worked.

static/css/teletext.css

@@ -465,10 +465,15 @@ a.tt-row:focus-visible .tt-row-sub { color: var(--tt-black); }
 .tt-empty { padding: 0 1ch; color: var(--ink-dim); }
 
 /* ── Fastext ────────────────────────────────────────────
-   The four coloured keys along the bottom of every teletext
-   page. Real navigation, not decoration: click one, or press
-   its initial. Deliberately NOT fixed to the viewport — it is
-   the last row of the page, where it always was. */
+   The four coloured keys. Real navigation, not decoration:
+   click one, or press its initial. Deliberately NOT fixed to
+   the viewport — it is a row of the page, where it always
+   was, not furniture bolted over it. On the index it closes
+   the page, under Now Showing/Just Added, because the index's
+   own body is already the full nav. Everywhere else — where
+   these four keys are the only nav on the page — it opens the
+   page, right under the header, so it doesn't need a scroll
+   to reach. */
 .fastext {
   display: grid;
   grid-template-columns: repeat(4, 1fr);
@@ -477,6 +482,9 @@ a.tt-row:focus-visible .tt-row-sub { color: var(--tt-black); }
   padding: 0 var(--gutter);
   gap: 1ch;
 }
+.fastext-top {
+  margin: var(--row) auto calc(var(--row) * 1.5);
+}
 .fastext a {
   display: flex;
   align-items: center;