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>

.htaccess

@@ -1,6 +1,8 @@
 DirectoryIndex index.php
 Options -Indexes
 
+SetEnvIf Authorization "(.*)" HTTP_AUTHORIZATION=$1
+
 <FilesMatch "^\.env">
     Require all denied
 </FilesMatch>
@@ -13,5 +15,6 @@ Options -Indexes
 
 <IfModule mod_rewrite.c>
     RewriteEngine On
+    RewriteRule ^api/mcp/user/?(.*)$ api/mcp/user/index.php [QSA,L]
     RewriteRule ^includes/ - [F,L]
 </IfModule>