feat: add Do Better Norge MCP server — token system, runtime API, interactive setup page

- UserMcpTokens: per-user SHA256-hashed token mint/validate/revoke (Plus/Pro only)
- DbnMcpRuntime: 19 MCP tools (search, ask, summarize, timeline, redact, translate,
  legal_analysis, korrespond, barnevernet_analyze, advocate_brief, deep_research,
  discrepancy_find, transcribe_audio, corpus_stats, list_documents, get_document,
  citation_graph, case_workbench_plan, save_to_case)
- api/mcp/user/: session/tools/invoke HTTP endpoints with Bearer token auth
- api/mcp-tokens.php: token create/revoke/list REST API
- mcp.php: interactive setup page with token management, 5-client config tabs,
  auto-fill on token creation, tool catalog grid, privacy notice
- account.php: simplified MCP section with link to mcp.php
- nav.php: MCP nav link
- .htaccess: Authorization header passthrough, MCP route rewrite, CORS

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

account.php

@@ -177,6 +177,18 @@ window.DBN_TOOLS_LANG = <?= json_encode($uiLang, JSON_UNESCAPED_UNICODE) ?>;
         <?php endif; ?>
     </section>
 
+<?php if ($isSso && $detail && in_array((string)($detail['tier'] ?? 'free'), ['plus', 'pro'], true)): ?>
+    <section class="account-section">
+        <p class="account-section__title">MCP access</p>
+        <p style="color:var(--muted,#667085); font-size:0.88rem; margin-top:0;">
+            Connect Claude, Cursor, and other AI tools to all 19 DBN legal preparation tools via MCP.
+        </p>
+        <a href="/mcp.php" class="account-upgrade-btn" style="display:inline-block; text-decoration:none; margin-top:0.75rem;">
+            Set up MCP →
+        </a>
+    </section>
+<?php endif; ?>
+
 <?php if ($detail): ?>
     <!-- ── Usage ────────────────────────────────────────────────── -->
     <section class="account-section">