perf: SEO improvements — defer d3.js, shorter title, Permissions-Policy

- Add defer to d3.v7.min.js in base.html — eliminates ~1.8s render
  blocking on every page (d3 only needed on user interaction)
- Shorten landing page title from 71 to 59 chars (SEO optimum: 30-60)
- Add Permissions-Policy security header (camera, microphone, geolocation)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app.py

@@ -791,6 +791,7 @@ def set_security_headers(response):
     response.headers['X-XSS-Protection'] = '1; mode=block'
     response.headers['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains'
     response.headers['Referrer-Policy'] = 'strict-origin-when-cross-origin'
+    response.headers['Permissions-Policy'] = 'camera=(), microphone=(), geolocation=(self)'
 
     # Freshness signal for SEO crawlers
     if response.content_type and 'text/html' in response.content_type and 'Last-Modified' not in response.headers:

templates/base.html

@@ -2596,7 +2596,7 @@
     </script>
 
     <!-- D3.js for Connections Map Modal -->
-    <script src="{{ url_for('static', filename='js/vendor/d3.v7.min.js') }}"></script>
+    <script src="{{ url_for('static', filename='js/vendor/d3.v7.min.js') }}" defer></script>
 
     <!-- Scroll Animations (Sprint 4) -->
     <script src="{{ url_for('static', filename='js/scroll-animations.js') }}" defer></script>

templates/landing.html

@@ -1,6 +1,6 @@
 {% extends "base.html" %}
 
-{% block title %}Norda Biznes Partner - Firmy Członkowskie Izby Gospodarczej | Wejherowo{% endblock %}
+{% block title %}Norda Biznes — Katalog Firm Członkowskich Izby Gospodarczej{% endblock %}
 
 {% block meta_description %}Katalog {{ total_companies }} firm członkowskich Izby Gospodarczej Norda Biznes - Wejherowo, powiat wejherowski i województwo pomorskie. Networking i współpraca biznesowa.{% endblock %}