feat: add host-provided module object storage

`manifest.storage.buckets` has existed since manifest version 1 and meant
nothing — discovery validated it and no code read it. This turns it into a
real capability, which is what stands between Announcements and the module
system: that product currently fetches a hardcoded LAN S3 endpoint, parses
ListObjectsV2 XML by hand, and hands the browser direct object URLs.

- A module declares a logical bucket and receives a scoped facade at
  `context.storage` — list, head, get, put, delete. The contract names no
  provider: no endpoint, region, credential, or physical bucket is reachable
  from it, which is what lets the same module run under a future standalone
  host over its own or a shared S3-compatible service.
- Core's first provider speaks S3 through the AWS SDK. SeaweedFS is the
  deployment target (ADR 0004), never an API name. Probing the pinned image
  found `CreateBucket` reporting `BucketAlreadyExists` rather than AWS's
  `BucketAlreadyOwnedByYou`; treating only the AWS spelling as success would
  have failed every second boot. A live test pins it.
- Logical → physical mapping is deterministic and collision-safe: an
  installation prefix, the module and bucket ids joined by `--` (which cannot
  occur inside either identifier, so `a-b`+`c` and `a`+`b-c` cannot collide),
  and a digest over the full untruncated identity. Two modules declaring
  `assets` always get separate namespaces; neither can see the physical name.
- Declaring a bucket is now a requirement: with no provider configured the
  module is `blocked · storage_unavailable` through ADR 0028's existing
  resolver, propagating to required dependents. An installation with no object
  storage stays a complete deployment.
- Binding availability is not provider health. Eligibility asks whether
  storage is configured, never whether it answered; bucket creation is lazy on
  first use so a storage outage cannot stop the platform booting; a running
  module whose store blinks stays running and retries. Nothing deletes a
  bucket.
- Credentials are deployment-supplied, never persisted, never routed through
  module configuration, and never visible to modules, module UI, diagnostics,
  or API responses. Provider errors translate to a closed code set carrying no
  endpoint, bucket, request id, or XML.
- Retires ADR 0029's transitional `bucket` configuration key. No manifest
  version change. The template declares no bucket, so it still runs without S3.

See ADR 0030.

Co-Authored-By: Claude Opus 5 <[email protected]>

tests/infrastructure.test.ts

@@ -138,8 +138,15 @@ describe("development infrastructure", () => {
     );
     expect(source).toContain('source "$repository_root/scripts/lib/compose-job-network.sh"');
     expect(source).toContain('export POSTGRES_PORT="0"');
-    expect(source).toContain("up --detach --wait --wait-timeout 120 postgres");
+    // Both live services come from the repository's own pinned Compose file, so the integration
+    // suites exercise exactly what a developer runs locally (ADR 0030 added the object-storage half).
+    expect(source).toContain("up --detach --wait --wait-timeout 180 postgres object-storage");
     expect(source).toContain(`compose_job_network_connect postgres "\${compose[@]}"`);
+    expect(source).toContain(`compose_job_network_connect object-storage "\${compose[@]}"`);
+    // The storage suite receives an endpoint and the same credentials the service was started with,
+    // and never a hardcoded host.
+    expect(source).toContain("EKKLESIA_TEST_STORAGE_ENDPOINT=");
+    expect(source).toContain("EKKLESIA_TEST_STORAGE_ACCESS_KEY=");
     expect(source).toContain('database_host="postgres"');
     expect(source).toContain('database_port="5432"');
     expect(source).toContain('database_host="127.0.0.1"');