Organisationsvorlagen: ein ganzes Haus als importierbare Datei (#691)

- Core/Organisation/OrgTemplate: format, export, parse, structural checks.
  Export empties every credential (nested, name variants) and names it;
  a template that carries one is refused.
- OrgAdministration: ExportTemplate, PreviewTemplate (problems, warnings,
  every text in full), ImportTemplateAsync - only with confirmation, units
  before agents, own workspace per unit, doctrines, model and budget factor
  overridable, templateOrigin on every unit and agent.
- Endpoints GET /organisation/template, POST .../preview, POST .../import;
  templates card in the organisation view.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClawdDotNet.Core/Config/UnitConfig.cs

@@ -70,6 +70,10 @@ public sealed class UnitConfig
     /// </summary>
     [JsonPropertyName("votes")]
     public UnitVotes? Votes { get; set; }
+
+    /// <summary>#691: The template the unit came from — its texts and rules are someone else's.</summary>
+    [JsonPropertyName("templateOrigin")]
+    public string? TemplateOrigin { get; set; }
 }
 
 /// <summary>