fix(#195): Implement RLS context helpers consistently across all services
Added workspace context management to PrismaService:
- setWorkspaceContext(userId, workspaceId, client?) - Sets session variables
- clearWorkspaceContext(client?) - Clears session variables
- withWorkspaceContext(userId, workspaceId, fn) - Transaction wrapper
Extended db-context.ts with workspace-scoped helpers:
- setCurrentWorkspace(workspaceId, client)
- setWorkspaceContext(userId, workspaceId, client)
- clearWorkspaceContext(client)
- withWorkspaceContext(userId, workspaceId, fn)
All functions use SET LOCAL for transaction-scoped variables (connection pool safe).
Added comprehensive tests (11 passing unit tests).
Fixes #195
Co-Authored-By: Claude Sonnet 4.5 <[email protected]>