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-sha256-tradeoff.md

@@ -0,0 +1,37 @@
+---
+id: document-sha256-tradeoff
+name: Document SHA-256 API Key Hashing Trade-Off
+status: completed
+depends_on: []
+scope: narrow
+risk: low
+impact: isolated
+level: implementation
+---
+
+## Description
+
+W13: API keys are stored as SHA-256 hashes — a fast hash, not a deliberately slow KDF (bcrypt/Argon2). If the database is compromised, SHA-256 hashes can be brute-forced faster than slow hashes. However, API keys are high-entropy machine-generated strings (128-bit+), making brute-force infeasible even with a fast hash. No ADR documents this trade-off.
+
+Add documentation to ADR-010 or relevant section explaining why SHA-256 is acceptable for high-entropy API keys.
+
+## Acceptance Criteria
+
+- [ ] ADR-010 (or a new ADR) documents the SHA-256 vs KDF trade-off
+- [ ] Rationale includes: high-entropy keys make brute-force infeasible, O(1) verification latency at high throughput
+- [ ] Explicitly states this is acceptable because keys are machine-generated, unlike human passwords
+- [ ] Cross-reference from `identity.md` api_keys section to the ADR
+
+## References
+
+- docs/reviews/storage-architecture-review-2026-04-21.md#W13
+- docs/architecture/storage/identity.md:74
+- docs/decisions/ADR-010
+
+## Notes
+
+> To be filled by implementation agent
+
+## Summary
+
+> To be filled on completion