feat(studio): store-side source filter, provenance pills, one-click recommended sources (v0.29.0)

The Store is now the centre of capability discovery — provider
configuration moves out of Settings into the Store itself.
Three changes work together:

1. Source filter chips next to the existing status chips:
   All sources / Native / MCP / n8n. Applied client-side after
   the hub returns results so toggling is instant. The result
   count and the "Clear filters" reset both account for the
   source filter too.

2. Per-card provenance pill (`_ProvenancePill`): shows whether
   each entry is native, mcp · <provider>, or n8n · <provider>
   so the operator can triage the source at a glance — same
   role the "verified" badge plays in commercial app stores.

3. `_RecommendedSourcesStrip` replaces the older
   `_FederationNudge`. Renders curated public MCP servers
   (DeepWiki, Semgrep) as one-click cards with an inline
   `[+ Add]` button — no Settings detour, no form. Both servers
   are HTTPS Streamable-HTTP, no API key, no subprocess.
   Useful AI was considered but its 340+ tools would drown the
   index — kept out of the curated list. The strip auto-hides
   the moment any federated entry exists.

Removed the now-orphaned storeFederationNudge* ARB keys.

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

pubspec.yaml

@@ -1,7 +1,7 @@
 name: fai_studio
 description: "F∆I Studio — desktop GUI for the F∆I hub"
 publish_to: 'none'
-version: 0.28.0
+version: 0.29.0
 
 environment:
   sdk: ^3.11.0-200.1.beta