feat: per-template metadata — eliminate meta.json merge conflicts

- move each template's metadata to blueprints/<id>/meta.json (442 files, byte-identical roundtrip with the old root meta.json)
- generate the served meta.json at build time into app/public/meta.json (gitignored); pnpm dev/build run the generator first
- CI validates every blueprints/<id>/meta.json via generate-meta.js --check (required fields, id/folder match, logo exists, folder<->meta bidirectionality) and rejects any committed root meta.json
- remove root meta.json, dedupe-and-sort-meta.js and build-scripts/process-meta.js (obsolete)
- update CONTRIBUTING.md, AGENTS.md and README.md

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

blueprints/triggerdotdev/meta.json

@@ -0,0 +1,16 @@
+{
+  "id": "triggerdotdev",
+  "name": "Trigger.dev",
+  "version": "v3",
+  "description": "Trigger is a platform for building event-driven applications.",
+  "logo": "triggerdotdev.svg",
+  "links": {
+    "github": "https://github.com/triggerdotdev/trigger.dev",
+    "website": "https://trigger.dev/",
+    "docs": "https://trigger.dev/docs"
+  },
+  "tags": [
+    "event-driven",
+    "applications"
+  ]
+}