feat: guided-setup wizard — localized explained options + plain-language plan

Reworks the Setup-Assistent toward the zero-learning-curve bar
(docs/architecture/guided-setup.md, phase 1.1):

- Every scenario/intent/target choice is now a localized option CARD
  with a one-line plain-language explanation of what it configures
  (DE+EN, Sie-form) — replacing the bare dropdowns whose labels were
  English enum humanizations ('Regulated Production', 'This Laptop').
- Three explained steps with a 'Schritt n von 3' progress line
  (stakes → task → environment); the two adaptive toggles move to the
  last step in plain language (no 'air-gapped' jargon).
- The review step renders a localized PLAIN-LANGUAGE summary built
  from 'chain init --answers --plan-json' (the structured SetupPlan) —
  'Ch∆In richtet einen regulierten Betrieb ein: signierte Module
  verlangt · … · geändert wird nur ~/.chain/config.yaml' — instead of
  echoing the CLI's English prose. Warns when an existing config will
  be overwritten. After apply: a plain 'Fertig' + next steps.

flutter analyze clean; widget tests for the step flow + German option
labels. Remaining per plan: clickable follow-up actions, signature
dead-end fix, placement/auto-open, and the LLM free-text path.

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

lib/l10n/app_localizations_en.dart

@@ -2967,4 +2967,180 @@ class AppLocalizationsEn extends AppLocalizations {
 
   @override
   String get sealedLeave => 'Leave';
+
+  @override
+  String setupStepOf(int n, int total) {
+    return 'Step $n of $total';
+  }
+
+  @override
+  String get setupStep1Title => 'What are the stakes?';
+
+  @override
+  String get setupStep2Title => 'What do you want to do first?';
+
+  @override
+  String get setupStep3Title => 'Where will it run?';
+
+  @override
+  String get setupReviewTitle => 'This is what Ch∆In will set up';
+
+  @override
+  String get setupChooseFreeText => 'Or just describe what you want to do';
+
+  @override
+  String get setupScenTryingOut => 'Just trying it out';
+
+  @override
+  String get setupScenTryingOutSub =>
+      'A relaxed workspace on this machine — no signing, no audit locking.';
+
+  @override
+  String get setupScenTeamHub => 'A shared team hub';
+
+  @override
+  String get setupScenTeamHubSub =>
+      'A secured hub for several people — signed modules, resource limits.';
+
+  @override
+  String get setupScenRegulated => 'Regulated production';
+
+  @override
+  String get setupScenRegulatedSub =>
+      'Signed modules, a complete tamper-evident audit trail, and a human approval before every AI step.';
+
+  @override
+  String get setupScenBuildModules => 'Building modules';
+
+  @override
+  String get setupScenBuildModulesSub =>
+      'A developer setup for writing and testing your own modules.';
+
+  @override
+  String get setupIntentHello => 'Run the hello example';
+
+  @override
+  String get setupIntentHelloSub => 'Just see one flow run end to end.';
+
+  @override
+  String get setupIntentExtract => 'Extract text from documents';
+
+  @override
+  String get setupIntentExtractSub =>
+      'Pull plain text out of PDF and DOCX files.';
+
+  @override
+  String get setupIntentExtractSummarize => 'Extract and summarize';
+
+  @override
+  String get setupIntentExtractSummarizeSub =>
+      'Extract text, then summarize it.';
+
+  @override
+  String get setupIntentClassify => 'Sort incoming documents';
+
+  @override
+  String get setupIntentClassifySub =>
+      'Extract text, then classify it with an AI step.';
+
+  @override
+  String get setupIntentBuildModule => 'Build my own module';
+
+  @override
+  String get setupIntentBuildModuleSub => 'Start from a module scaffold.';
+
+  @override
+  String get setupTargetLaptop => 'This computer';
+
+  @override
+  String get setupTargetLaptopSub =>
+      'Runs locally on the machine you are on now.';
+
+  @override
+  String get setupTargetHomeServer => 'An on-premise server';
+
+  @override
+  String get setupTargetHomeServerSub =>
+      'A server in your own house — starts on boot, runs in the background.';
+
+  @override
+  String get setupTargetAirgapped => 'A fully local server (no internet)';
+
+  @override
+  String get setupTargetAirgappedSub =>
+      'An isolated server with no internet — the strictest, most private posture.';
+
+  @override
+  String get setupTargetContainer => 'A container';
+
+  @override
+  String get setupTargetContainerSub =>
+      'Docker or Podman, with a ready-made compose snippet.';
+
+  @override
+  String get setupApprovalPlain =>
+      'Ask a person for approval before every AI step';
+
+  @override
+  String get setupDataLocalPlain =>
+      'Data must never leave the building (fully local)';
+
+  @override
+  String get setupPlanIntroDev => 'Ch∆In sets up a straightforward workspace.';
+
+  @override
+  String get setupPlanIntroEnterprise =>
+      'Ch∆In sets up a secured operation for a team.';
+
+  @override
+  String get setupPlanIntroAirgapped =>
+      'Ch∆In sets up a fully local, regulated operation.';
+
+  @override
+  String get setupPlanSignatures => 'Only signed modules are allowed.';
+
+  @override
+  String get setupPlanWorm =>
+      'The audit log is additionally sealed tamper-proof (WORM).';
+
+  @override
+  String get setupPlanApproval =>
+      'Before every AI step, the system asks a person for approval.';
+
+  @override
+  String setupPlanModules(String modules) {
+    return 'These modules are prepared: $modules.';
+  }
+
+  @override
+  String setupPlanFlow(String flow) {
+    return 'An example flow “$flow” is created.';
+  }
+
+  @override
+  String setupPlanFileChanged(String path) {
+    return 'Only one file is changed: $path.';
+  }
+
+  @override
+  String get setupPlanOverwriteWarn =>
+      'An existing configuration will be overwritten.';
+
+  @override
+  String get setupApplied => 'Done — Ch∆In is set up.';
+
+  @override
+  String get setupNextTitle => 'Next steps';
+
+  @override
+  String get setupNextHubStart => 'Start the hub';
+
+  @override
+  String get setupNextInstall => 'Install the modules';
+
+  @override
+  String get setupNextRunFlow => 'Run the example flow';
+
+  @override
+  String get setupStartCta => 'Get started in 3 questions';
 }