F2: Client-Project binding (assign/reassign projects to clients)

[rororowyourboat]

Summary

Establish a parent-child relationship between Clients and Projects so every Project can be organizationally anchored to a Client.

Scope

• Extend ProjectCreateCommand schema with optional(ClientId) field
• Add new commands: project.client.assign, project.client.reassign, project.client.unassign
• Add new events: project.client.assigned, project.client.reassigned (carries previousClientId), project.client.unassigned
• Add clientId column to projection_projects table (nullable, new migration)
• Update OrchestrationProject schema with Schema.optional(Schema.NullOr(ClientId)) and Schema.withDecodingDefault(() => null) for backward compatibility
• Update decider to validate target Client exists and is active on assign/reassign
• Update projector to set clientId on project projection
• Handle cascade on client.deleted: unassign all Projects belonging to that Client

Constraints

• A Project may have at most one clientId at any time
• Assigning to an archived or deleted Client is rejected
• Reassign to same Client is a no-op (no event emitted)
• Creating a Project without clientId is still valid (appears in "Unassigned")

Key files to modify

• packages/contracts/src/orchestration.ts — extend ProjectCreateCommand, add new command/event types
• apps/server/src/orchestration/decider.ts — new command cases
• apps/server/src/orchestration/projector.ts — new event cases + cascade logic
• apps/server/src/persistence/Migrations/ — new migration adding client_id column
• apps/server/src/persistence/Layers/ProjectionProjects.ts — update SQL queries

Dependencies

• F1 (Client entity must exist first)

Acceptance criteria

• New projects can be created with a clientId
• Existing projects without clientId continue to work (backward compat)
• Can assign an unassigned project to a Client
• Can reassign a project from one Client to another
• Can unassign a project (returns to "Unassigned")
• Assigning to archived/deleted Client is rejected
• Deleting a Client unassigns its Projects

[rororowyourboat]

Implemented in feat/sidebar-project-groups branch.