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.

src/s3/index.ts

@@ -0,0 +1,34 @@
+import { S3Client, PutObjectCommand, GetObjectCommand } from "@aws-sdk/client-s3";
+import { getSignedUrl } from "@aws-sdk/s3-request-presigner";
+
+const accountId = process.env.R2_ACCOUNT_ID ?? "";
+const bucket = process.env.R2_BUCKET ?? "continuum";
+
+export const s3 = new S3Client({
+  region: "auto",
+  endpoint: process.env.R2_ENDPOINT ?? `https://${accountId}.r2.cloudflarestorage.com`,
+  credentials: {
+    accessKeyId: process.env.R2_ACCESS_KEY_ID ?? "",
+    secretAccessKey: process.env.R2_SECRET_ACCESS_KEY ?? "",
+  },
+});
+
+/** Presigned PUT for clients uploading a G-code/3MF file directly to R2. */
+export async function getUploadUrl(key: string, contentType = "application/octet-stream", expiresInSeconds = 900) {
+  const command = new PutObjectCommand({ Bucket: bucket, Key: key, ContentType: contentType });
+  return getSignedUrl(s3, command, { expiresIn: expiresInSeconds });
+}
+
+/** Presigned GET for the edge proxy to download a job file over LAN via FTPS relay or direct fetch. */
+export async function getDownloadUrl(key: string, expiresInSeconds = 900) {
+  const command = new GetObjectCommand({ Bucket: bucket, Key: key });
+  return getSignedUrl(s3, command, { expiresIn: expiresInSeconds });
+}
+
+export function jobFileKey(farmId: string, jobId: string, fileName: string) {
+  return `farms/${farmId}/jobs/${jobId}/${fileName}`;
+}
+
+export function frameKey(farmId: string, printerId: string, frameId: string) {
+  return `farms/${farmId}/printers/${printerId}/frames/${frameId}.jpg`;
+}