feat(studio): plain-language store, bottom-anchored ask bar (v0.33.0)

The store had three structural problems flagged in user
feedback:

1. "Lernkurve zu hoch — alle bridge, debug, alpha, planned,
   keiner weiß was das heißt." Wire-level enum values bled
   through into the UI: `bridge`, `debug`, `published`,
   `alpha`, `planned`. Operators don't share the data model.

2. "Filter / Kategorien sollten oben in die Leiste neben Store
   zum ausklappen, der Body soll übersichtlicher werden." A
   chip-row plus category strip plus result-count line ate a
   full row of viewport on every screen.

3. "Suche passt besser an den unteren Bildschirmrand." The
   chat-style ask bar belongs at the bottom — Claude / ChatGPT
   / Slack pattern — not at the top where it competes with
   the Today hero.

Plus: "Es gibt noch ganz viele overflows in den Beschreibungen."

Changes:

- Plain-language display names. New ARB keys for category
  labels (Connectors / Sample modules / AI models / Storage /
  Channels / Authentication / Orchestration / …) and updated
  status values (stable / experimental / coming soon). Wire
  ids stay in StoreEntry, RPCs, seed.yaml — only the rendered
  pills and dropdowns get translated. Helpers
  `_categoryDisplayName` and `_statusDisplayName` keep the
  mapping in one place.

- Toolbar moves into the AppBar. The new `_CategoryDropdown`
  hosts the category picker as a popup-menu with localised
  labels; the existing `_FilterButton` lives next to it; the
  reload icon stays where it always was. The body no longer
  carries any chip strip or result-count line.

- Bottom-anchored `_AskBar`. The Scaffold body becomes a
  Column of `Expanded(scrollable content)` plus a pinned
  composer row at the foot of the viewport, with a top
  divider matching the chat-input pattern of modern AI
  assistants. AI answers now render at the top of the scroll
  (above the Today-Hero) so the operator sees them right
  after submitting the question at the bottom.

- Overflow sweep on descriptions. Today-Hero header row
  becomes a Wrap (badge + deck flow naturally on narrow
  windows), the title is bound to 3 lines, the body to 6.
  Card category text gets `maxLines: 1, ellipsis` in both
  StoreCard and FeaturedTile. Recommended-source card title
  gets the same treatment.

- Better toast for the "added but zero capabilities" path.
  When MCP discovery succeeds but returns no tools (typical
  Streamable-HTTP servers without Mcp-Session-Id support, or
  servers that need `notifications/initialized`), the toast
  now explains the situation in plain language and points
  the operator at Settings → MCP Clients to retry. Old
  pluralised toast still fires when N > 0.

Hub-side `notifications/initialized` for HTTP MCP and
Mcp-Session-Id support are out of scope for this commit;
tracked as a separate fai_hub follow-up.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_localizations_en.dart

@@ -394,17 +394,53 @@ class AppLocalizationsEn extends AppLocalizations {
   String get storeStatusAll => 'All';
 
   @override
-  String get storeStatusPublished => 'Published';
+  String get storeStatusPublished => 'stable';
 
   @override
-  String get storeStatusAlpha => 'Alpha';
+  String get storeStatusAlpha => 'experimental';
 
   @override
-  String get storeStatusPlanned => 'Planned';
+  String get storeStatusPlanned => 'coming soon';
 
   @override
   String get storeInstalledOnly => 'Installed';
 
+  @override
+  String get storeCategoryLabel => 'Category';
+
+  @override
+  String get storeCategoryAll => 'All categories';
+
+  @override
+  String get storeCategoryBridge => 'Connectors';
+
+  @override
+  String get storeCategoryDebug => 'Sample modules';
+
+  @override
+  String get storeCategoryText => 'Text';
+
+  @override
+  String get storeCategoryLlm => 'AI models';
+
+  @override
+  String get storeCategorySystem => 'System';
+
+  @override
+  String get storeCategoryAuth => 'Authentication';
+
+  @override
+  String get storeCategoryStorage => 'Storage';
+
+  @override
+  String get storeCategoryChannel => 'Channels';
+
+  @override
+  String get storeCategoryWeb => 'Web';
+
+  @override
+  String get storeCategoryOrchestrator => 'Orchestration';
+
   @override
   String storeNResults(int n) {
     String _temp0 = intl.Intl.pluralLogic(
@@ -613,6 +649,11 @@ class AppLocalizationsEn extends AppLocalizations {
     return 'Added $name — $n federated $_temp0.';
   }
 
+  @override
+  String storeProviderAddedZeroToast(String name) {
+    return '$name registered, but the server returned no capabilities yet. Open Settings → MCP Clients to retry discovery or check the server.';
+  }
+
   @override
   String storeProviderAddFailed(String name, String error) {
     return 'Could not add $name: $error';