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.

templates/discover.html

@@ -1,11 +1,40 @@
 {% extends "_shell.html" %}
-{% from "_macros.html" import tile %}
+{% from "_macros.html" import tile, service_error %}
 {% block title %}P103 Discover{% endblock %}
 
 {% block content %}
   <h1 class="tt-dh bloom tt-masthead">DISCOVER</h1>
   <p class="tt-empty">Popular right now, with anything already in library filtered out.</p>
 
+  {#- Search sits at the top for the same reason it does on Library: a
+      title in mind is the common case. This one asks Ombi, which already
+      sits in front of TheMovieDB/TVDB, then lets you add straight to
+      Radarr/Sonarr from the result. -#}
+  <form class="tt-search" action="{{ request.script_root }}/discover" method="get" role="search">
+    <label class="visually-hidden" for="q">Search Ombi for a title</label>
+    <input class="tt-input" type="search" id="q" name="q" value="{{ q }}"
+           placeholder="SEARCH TO ADD" autocomplete="off" spellcheck="false">
+    <button class="tt-btn" type="submit">Search</button>
+  </form>
+
+  {% if search %}
+    <div class="tt-field">
+      <span>Results</span>
+      <span class="tt-field-meta">&ldquo;{{ q }}&rdquo;</span>
+    </div>
+    {% if search.status != 'ok' %}
+      {{ service_error('Ombi', search.error) }}
+    {% elif search.results %}
+      <div class="tt-tiles">
+        {% for it in search.results %}
+          {{ tile(it.title, it.kind ~ (' · Held' if it.held else ''), it.poster, it.year, ('' if it.held else '+ Add'), it.target) }}
+        {% endfor %}
+      </div>
+    {% else %}
+      <p class="tt-empty">No matches for &ldquo;{{ q }}&rdquo;.</p>
+    {% endif %}
+  {% endif %}
+
   <div class="tt-field">
     <span>Films</span>
     <span class="tt-field-meta">{{ rt_movies | length }} not in library</span>