Phase 1: PeerTube plugin and recon_domains module

Single source of truth for the 18 RECON knowledge domains mapped to
PeerTube category IDs 100-117. Replaces duplicate VALID_DOMAINS sets
in enricher.py and embedder.py with imports from lib/recon_domains.py.

Includes PeerTube plugin (peertube-plugin-recon-domains) that registers
custom categories via videoCategoryManager.addConstant(), and a parity
test to verify constants match between RECON and the PeerTube API.

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

peertube-plugin/peertube-plugin-recon-domains/package.json

@@ -0,0 +1,20 @@
+{
+  "name": "peertube-plugin-recon-domains",
+  "version": "1.0.0",
+  "description": "Registers 18 RECON knowledge domains as PeerTube video categories (IDs 100-117)",
+  "engine": {
+    "peertube": ">=6.0.0"
+  },
+  "keywords": [
+    "peertube",
+    "plugin"
+  ],
+  "homepage": "https://forge.echo6.co/matt/recon",
+  "author": "Echo6",
+  "license": "MIT",
+  "library": "./main.js",
+  "staticDirs": {},
+  "css": [],
+  "clientScripts": [],
+  "translations": {}
+}