Refactor to local-first architecture on Hetzner NVMe

Remove distributed R2/Iceberg/SSH pipeline architecture in favor of
local subprocess execution with NVMe storage. Landing data backed up
to R2 via rclone timer.

- Strip Iceberg catalog, httpfs, boto3, paramiko, prefect, pyarrow
- Pipelines run via subprocess.run() with bounded timeouts
- Extract writes to {LANDING_DIR}/psd/{year}/{month}/{etag}.csv.gzip
- SQLMesh reads LANDING_DIR variable, writes to DUCKDB_PATH
- Delete unused provider stubs (ovh, scaleway, oracle)
- Add rclone systemd timer for R2 backup every 6h
- Update supervisor to run pipelines with env vars

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

infra/backup/rclone.conf.example

@@ -0,0 +1,14 @@
+# Cloudflare R2 remote for landing data backup
+# Copy to /root/.config/rclone/rclone.conf and fill in credentials
+#
+# Get credentials from: Cloudflare Dashboard → R2 → Manage R2 API Tokens
+# Or from Pulumi ESC: esc env open beanflows/prod --format shell
+
+[r2]
+type = s3
+provider = Cloudflare
+access_key_id = <R2_ACCESS_KEY_ID>
+secret_access_key = <R2_SECRET_ACCESS_KEY>
+endpoint = https://<CLOUDFLARE_ACCOUNT_ID>.r2.cloudflarestorage.com
+acl = private
+no_check_bucket = true