feat(dashboard): add corpus dashboard at /dashboard/

Full private corpus dashboard for tools.dobetternorge.no users — each SSO
account gets an auto-provisioned CaveauAI tenant (clients row, corpus) on
first visit. Includes upload (file/paste/URL), RAG chat with SSE streaming
and citation chips, document CRUD, FalkorDB graph relations tab, and
improved save-from-tool flow with tag/preview support.

- dashboard/{index,documents,document,upload,chat,settings}.php
- api/dashboard/{corpus-init,documents,upload,ingest-status,chat-stream,
  save-from-tool,graph}.php
- includes/{CorpusProvision,layout_dashboard,layout_dashboard_footer}.php
- assets/css/dashboard.css  assets/js/corpus-save.js (routing upgrade)
- includes/{bootstrap,layout}.php extended for dashboard provisioning

Migration 141 (clients.dbn_sso_uid + import_method enum) applied on chloe.

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

includes/layout_dashboard_footer.php

@@ -0,0 +1,31 @@
+            </div><!-- /dash-main__body -->
+        </main><!-- /dash-main -->
+    </div><!-- /dash-layout -->
+</div><!-- /dash-shell -->
+
+<script src="/assets/js/tools.js" defer></script>
+<?php if (!empty($extraScripts) && is_array($extraScripts)): foreach ($extraScripts as $extraScript): ?>
+<script src="<?= htmlspecialchars((string)$extraScript) ?>" defer></script>
+<?php endforeach; endif; ?>
+<script src="/assets/js/corpus-save.js" defer></script>
+
+<dialog id="save-corpus-dialog" class="save-corpus-dialog">
+  <form method="dialog" id="save-corpus-form">
+    <h3>Save to corpus</h3>
+    <p class="save-corpus-hint">This will be indexed and searchable in your private corpus.</p>
+    <label>
+      <span>Title <span aria-hidden="true">*</span></span>
+      <input id="save-corpus-title" type="text" required autocomplete="off">
+    </label>
+    <label>
+      <span>Tags <span class="save-corpus-optional">(comma-separated)</span></span>
+      <input id="save-corpus-tags" type="text" placeholder="e.g. barnevern, 2024, kjennelse">
+    </label>
+    <menu>
+      <button type="submit" class="btn-primary">Save</button>
+      <button type="button" id="save-corpus-cancel">Cancel</button>
+    </menu>
+  </form>
+</dialog>
+</body>
+</html>