Fix remaining critical, high, and medium issues from 4-perspective review

Critical fixes:
- Fix rating clamp range 1-10 → 1-5 (actual scale)
- Add `ietf ideas convergence` command (SequenceMatcher at 0.75 threshold)
- Fix "628 cross-org ideas" → 130 (verified from current DB) across 8 files

Security fixes:
- Sanitize FTS5 query input (strip special chars + boolean operators)
- Add rate limiting (10 req/min/IP) on Claude-calling endpoints
- Change <path:name> → <string:name> on draft routes

Codebase fixes:
- Add Database context manager (__enter__/__exit__)
- Wire false_positive filtering into queries (exclude by default in web UI)
- Fix Post 3 arithmetic ("~300" → "~409" distinct proposals)

Content & licensing:
- Add MIT LICENSE file
- Add IPR/FRAND notes (BCP 79, RFC 8179) to Posts 03 and 07
- Qualify "4:1 safety ratio" with monthly variation in 6 remaining files
- Add "Data as of March 2026" freeze-date headers to all 10 blog posts
- Hedge causal language in Post 04

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

src/webui/templates/idea_clusters.html

@@ -3,10 +3,12 @@
 
 {% block title %}Idea Clusters — IETF Draft Analyzer{% endblock %}
 
+{% block extra_head %}<script src="/static/js/plotly.min.js"></script>{% endblock %}
+
 {% block content %}
 <div class="mb-6">
     <h1 class="text-2xl font-bold text-white">Idea Clusters</h1>
-    <p class="text-slate-400 text-sm mt-1">Extracted ideas grouped by semantic similarity — enriched with WG and category data</p>
+    <p class="text-slate-400 text-sm mt-1">Extracted ideas grouped by semantic similarity — enriched with WG and category data. Ideas are embedded using Ollama (nomic-embed-text), then clustered via DBSCAN so that semantically related ideas from different drafts are grouped together. "Cross-WG" clusters indicate ideas that span multiple IETF working groups — potential coordination points.</p>
 </div>
 
 <div id="emptyState" class="hidden">