feat(errors): classify the install 'no store entry' failure

Even with the honest install badge the hub error stays reachable
(stale store snapshot, race with a store refresh, older hub). The
friendly-error mapper now gives it its own headline plus a hint
naming the three acquisition paths — local module install, adding
the providing store, configuring the MCP/n8n integration — in EN
and DE, with the verbatim hub message kept copyable. Matcher unit
tests EN+DE guard the classification.

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

lib/l10n/app_en.arb

@@ -77,6 +77,8 @@
   "errMcpUnreachableHint": "The MCP server didn't respond. Check the endpoint in Settings → Integrations and confirm it's running.",
   "errCapabilityNotInstalled": "Required capability is not installed.",
   "errCapabilityNotInstalledHint": "Open the flow's Text tab — the analyzer's Fix button installs the capability if it's in the store.",
+  "errNoStoreEntry": "No store entry provides this capability.",
+  "errNoStoreEntryHint": "Three ways to get it: install a local module (chain install --link <path>), add the store that provides it (Settings → Stores), or configure the integration (MCP/n8n) that supplies it. If it was just published, refresh the Store page first.",
   "welcomeDocClose": "Close",
   "welcomeDocFailedToLoad": "Could not load documentation: {error}",
   "@welcomeDocFailedToLoad": {