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>

data/reports/blog-series/01-gold-rush.md

@@ -2,6 +2,8 @@
 
 *Fifteen months ago, AI agents barely registered at the IETF. Today, nearly 1 in 10 new Internet-Drafts is about AI agents. We analyzed every one.*
 
+*Analysis based on IETF Datatracker data collected through March 2026. Counts and statistics reflect this snapshot.*
+
 ---
 
 For every Internet-Draft addressing how to keep an AI agent safe, roughly four are building new capabilities for it. That is the single most important number in this analysis.