🛠 Update BlockNote to remove uuid advisory

[baealex]

🎯 Goal

• Remove the transitive vulnerable uuid dependency pulled through BlockNote.
• Keep existing Markdown conversion behavior stable while applying the minimum safe BlockNote upgrade.

🛠️ Core Changes

• Updated BlockNote packages from 0.46.2 to 0.49.0.
• Adjusted the custom code block render prop type for the updated BlockNote React API.
• Preserved Markdown hard-break import behavior under the updated server editor.
• Refreshed the lockfile so uuid is no longer installed through BlockNote.

🧠 Key Decisions

• Chose 0.49.0 because it is the first checked BlockNote version that removes uuid.
• Avoided 0.51.x because its Markdown serializer changes existing export output broadly.
• Kept the change scoped to compatibility and security; no user-facing editor features were added.

🧪 Verification Guide

How to verify

1. Run pnpm audit --audit-level moderate.
2. Run pnpm --filter @ocean-brain/server test -- test/blocknote.test.ts.
3. Run pnpm --filter @ocean-brain/client type-check.
4. Run pnpm --filter @ocean-brain/server type-check.
5. Run pnpm lint.
6. Run pnpm build.

Expected result

• Audit reports no known vulnerabilities at moderate level.
• BlockNote Markdown conversion tests pass.
• Type-check, lint, and build pass.

✅ Checklist

• Lint completed
• Type-check completed
• Tests completed
• Documentation updated (if needed)