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>

src/materia/providers/__init__.py

@@ -1,7 +1,6 @@
-"""Cloud provider abstraction for worker management."""
+"""Cloud provider for worker management."""
 
 from dataclasses import dataclass
-from typing import Protocol
 
 
 @dataclass
@@ -14,35 +13,10 @@ class Instance:
     type: str
 
 
-class ProviderModule(Protocol):
-    def create_instance(
-        self: str,
-        instance_type: str,
-        ssh_key: str,
-        location: str | None = None,
-    ) -> Instance: ...
-
-    def destroy_instance(self: str) -> None: ...
-
-    def list_instances(self: str | None = None) -> list[Instance]: ...
-
-    def get_instance(self: str) -> Instance | None: ...
-
-    def wait_for_ssh(self: str, timeout: int = 300) -> bool: ...
-
-
-def get_provider(provider_name: str) -> ProviderModule:
+def get_provider(provider_name: str):
     if provider_name == "hetzner":
         from materia.providers import hetzner
+
         return hetzner
-    elif provider_name == "ovh":
-        from materia.providers import ovh
-        return ovh
-    elif provider_name == "scaleway":
-        from materia.providers import scaleway
-        return scaleway
-    elif provider_name == "oracle":
-        from materia.providers import oracle
-        return oracle
     else:
         raise ValueError(f"Unknown provider: {provider_name}")