Initial commit: Pokerface sprint planning poker for Jira

Full-stack app with Express/Socket.io backend, React frontend,
NATS JetStream for state, and Atlassian Jira OAuth integration.

Includes security hardening: NATS auth support, KV bucket TTL
enforcement, CAS retry for race conditions, error message
sanitization, and OAuth state stored in NATS KV.

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

.gitignore

@@ -0,0 +1,8 @@
+node_modules
+.env
+.DS_Store
+backend/node_modules
+frontend/node_modules
+backend/prisma/migrations
+frontend/dist
+backend/.env