Add 3 public Korrespond documentation pages with AI hero images

- korrespond-about.php: marketing/hype page with hero image, features,
  3-step pipeline, screenshot gallery, dbn-legal-agent LLM spotlight,
  authority coverage grid, and CTA strip
- korrespond-guide.php: step-by-step user guide covering mode selection,
  recipient body presets, output types, tone, all form fields, clarify
  gate, output columns, and Refine pass
- korrespond-tech.php: technical showcase — Hard-RAG pipeline diagram,
  corpus stats, CITE:N verification system, fine-tuned model details,
  formal citation style guide, privacy section
- 5 UI screenshots + 3 AI-generated hero images in assets/images/korrespond/
- korrespond.php: add "About · User guide · How it works" inline links
- preview.php: add korrespond to localizedContent (en+no) and samples;
  render doc-page links in preview CTA section for korrespond slug
- tools.css: +600 lines .kdoc-* CSS (hero, features, pipeline, guide
  steps, tech diagrams, finetune block, privacy block, stat cards)

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

korrespond.php

@@ -16,6 +16,14 @@ require_once __DIR__ . '/includes/layout.php';
                         <button type="button" class="lang-btn" data-lang="pl">&#127477;&#127473; PL</button>
                     </div>
 
+                    <div class="korr-doc-links">
+                        <a href="/korrespond-about.php" target="_blank">About this tool</a>
+                        <span aria-hidden="true">&middot;</span>
+                        <a href="/korrespond-guide.php" target="_blank">User guide</a>
+                        <span aria-hidden="true">&middot;</span>
+                        <a href="/korrespond-tech.php" target="_blank">How it works</a>
+                    </div>
+
                     <!-- Mode toggle -->
                     <div class="control-row" id="korrModeControl">
                         <span class="control-label">Mode</span>