fix(l10n): one term for capabilities, plain federation language

- 'Fähigkeiten' is the German lead term everywhere (welcome step 2,
  integrations panel, federation) — English jargon only as a
  parenthesized technical term on first mention
- 'Enrollment-Token' -> 'Registrierungs-Token', bootstrap label in
  plain words, CA spelled out, enrollment hint now formal address
- formality guard also rejects reader-addressed imperatives

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

lib/l10n/app_en.arb

@@ -86,8 +86,8 @@
   "welcomeChecklistBody": "Four steps to a working hub. Live state — refresh after changing anything.",
   "welcomeChecklistAi": "Configure System AI",
   "welcomeChecklistAiHint": "Settings → System AI. Required for the AI search and inline failure explanations.",
-  "welcomeChecklistMcp": "Add a public capability source",
-  "welcomeChecklistMcpHint": "Add an MCP source from the Store, or configure one under Settings → MCP Clients.",
+  "welcomeChecklistMcp": "Connect a public tool catalog",
+  "welcomeChecklistMcpHint": "Connects a public tool catalog (the technical term is MCP) — its capabilities then appear in the Store. Add one there, or under Settings → MCP Clients.",
   "welcomeChecklistModule": "Install a text module",
   "welcomeChecklistModuleHint": "Install a module from the Store — pick whichever category fits your work. Modules are sandboxed Ch∆In components.",
   "welcomeChecklistFlow": "Run a saved flow",
@@ -1182,7 +1182,7 @@
     }
   },
   "doctorSummaryPending": "pending",
-  "doctorSummaryChain": "{verified}/{total} chain",
+  "doctorSummaryChain": "{verified} of {total} events verified",
   "@doctorSummaryChain": {
     "placeholders": {
       "verified": {