chore(release): v3.1.0 — consolidate 3.0.10-3.0.14 + OpenClaw republish prep (#314)

- Bump plugin.json to 3.1.0
- CHANGELOG entry consolidating 3.0.10-3.0.14 dev cycle and noting OpenClaw republish
- Fix broken README link: skills/last30days/SKILL.md -> SKILL.md

Co-authored-by: Matt Van Horn <455140+mvanhorn@users.noreply.github.com>

.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "last30days",
-  "version": "3.0.14",
+  "version": "3.1.0",
   "description": "Research any topic across Reddit, X, YouTube, TikTok, Instagram, Hacker News, Polymarket, GitHub, and 5+ more sources. AI agent scores by upvotes, likes, and real money - not editors.",
   "author": {
     "name": "Matt Van Horn",