refactor(docs): migrate existing content to v1 legacy structure

- Move all existing docs content (concepts, project, solution) to /docs/v1/
- Add legacy banner component to warn users about archived documentation
- Create v1 index page with legacy notice and redirect guidance
- Implement automatic banner display for all v1 paths
- Preserve all original content for reference during migration

This enables incremental content migration while maintaining access to
original documentation.

layouts/docs/single.html

@@ -0,0 +1,17 @@
+{{ define "main" }}
+{{ partial "legacy-banner.html" . }}
+<div class="td-content">
+	<h1>{{ .Title }}</h1>
+	{{ with .Params.description }}<div class="lead">{{ . | markdownify }}</div>{{ end }}
+	{{ .Content }}
+        {{ if (and (not .Params.hide_feedback) (.Site.Params.ui.feedback.enable) (.Site.GoogleAnalytics)) }}
+		{{ partial "feedback.html" .Site.Params.ui.feedback }}
+                <br />
+        {{ end }}
+        {{ if (.Site.DisqusShortname) }}
+                <br />
+                {{ partial "disqus-comment.html" . }}
+        {{ end }}
+	<div class="text-muted mt-5 pt-3 border-top">{{ partial "page-meta-lastmod.html" . }}</div>
+</div>
+{{ end }}

layouts/partials/legacy-banner.html

@@ -0,0 +1,13 @@
+{{ if or (hasPrefix .RelPermalink "/docs/v1/") (hasPrefix .File.Path "docs/v1/") }}
+<div class="alert alert-warning legacy-banner" role="alert">
+  <h4 class="alert-heading">
+    <i class="fa fa-archive"></i> Legacy Documentation (v1)
+  </h4>
+  <p class="mb-0">
+    You are viewing archived documentation. 
+    {{ $newPath := replace .RelPermalink "/v1/" "/" }}
+    {{ $newPath = replace $newPath "/docs/docs/" "/docs/" }}
+    Please check if there is an <a href="{{ $newPath }}" class="alert-link">updated version</a> available.
+  </p>
+</div>
+{{ end }}