Setup repo: migrate architecture specs, code stubs, and tasks from alkhub_ts

Copy architecture docs, ADRs, storage domain specs, research, reviews,
and 56 storage architecture tasks from the alkhub_ts monorepo. Adapt for
standalone @alkdev/hub repo structure (src/ not packages/hub/).

Sanitize all sensitive information:
- Replace private IPs (10.0.0.1) with localhost defaults
- Remove internal server hostnames (dev1, ns528096)
- Replace /workspace/ private paths with npm package references
- Remove hardcoded credentials from examples
- Rewrite infrastructure.md without private network details

Add Deno project scaffolding: deno.json (pinned deps), .gitignore,
AGENTS.md, entry point. Migrate existing code stubs (crypto, config
types, logger) with updated import paths.

tasks/architecture/storage/document-api-key-expiration-behavior.md

@@ -0,0 +1,34 @@
+---
+id: document-api-key-expiration-behavior
+name: Document API Key Expiration Behavior
+status: completed
+depends_on: []
+scope: single
+risk: trivial
+impact: isolated
+level: implementation
+---
+
+## Description
+
+**S05**: Does an expired API key return "key expired" or a generic "authentication failed"? Without documentation, implementers may leak key state to attackers by returning specific error messages. Recommend documenting that expired keys return a generic authentication failure to avoid information disclosure.
+
+## Acceptance Criteria
+
+- [ ] `identity.md` or `services.md` documents API key expiration error behavior
+- [ ] Recommendation stated: expired keys return generic auth failure, not "key expired"
+- [ ] Consistent with ADR-008 (key rotation) and keypal integration notes
+
+## References
+
+- docs/reviews/storage-architecture-review-2026-04-21.md#S05
+- docs/architecture/storage/identity.md (api_keys table)
+- docs/decisions/ADR-008
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion