Initial boilerplate scaffold for continuum-backend

Bun + ElysiaJS control plane: Drizzle/Postgres schema (printers, farms,
print_jobs, pgvector frame_embeddings), R2 presigned URLs, Redis Streams
frame ingestion queue, REST routes, and the /ws/edge/v1 edge-gateway
WebSocket uplink.

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

.env.example

@@ -0,0 +1,22 @@
+PORT=3000
+
+# Postgres, routed through pgCat/PgBouncer
+DATABASE_URL=postgres://continuum:continuum@localhost:6432/continuum
+DATABASE_POOL_MAX=10
+
+# Redis (state + streams)
+REDIS_URL=redis://localhost:6379
+
+# Cloudflare R2 (S3-compatible)
+R2_ACCOUNT_ID=
+R2_BUCKET=continuum
+R2_ENDPOINT=
+R2_ACCESS_KEY_ID=
+R2_SECRET_ACCESS_KEY=
+
+# Supabase Auth
+SUPABASE_JWT_SECRET=
+SUPABASE_URL=
+
+# Minted for continuum-proxy edge gateways via POST /auth/edge-token
+EDGE_JWT_SECRET=