feat(#89): implement COMMAND message type for federation

Implements federated command messages following TDD principles and
mirroring the QueryService pattern for consistency.

## Implementation

### Schema Changes
- Added commandType and payload fields to FederationMessage model
- Supports COMMAND message type (already defined in enum)
- Applied schema changes with prisma db push

### Type Definitions
- CommandMessage: Request structure with commandType and payload
- CommandResponse: Response structure with correlation
- CommandMessageDetails: Full message details for API responses

### CommandService
- sendCommand(): Send command to remote instance with signature
- handleIncomingCommand(): Process incoming commands with verification
- processCommandResponse(): Handle command responses
- getCommandMessages(): List commands for workspace
- getCommandMessage(): Get single command details
- Full signature verification and timestamp validation
- Error handling and status tracking

### CommandController
- POST /api/v1/federation/command - Send command (authenticated)
- POST /api/v1/federation/incoming/command - Handle incoming (public)
- GET /api/v1/federation/commands - List commands (authenticated)
- GET /api/v1/federation/commands/:id - Get command (authenticated)

## Testing
- CommandService: 15 tests, 90.21% coverage
- CommandController: 8 tests, 100% coverage
- All 23 tests passing
- Exceeds 85% coverage requirement
- Total 47 tests passing (includes command tests)

## Security
- RSA signature verification for all incoming commands
- Timestamp validation to prevent replay attacks
- Connection status validation
- Authorization checks on command types

## Quality Checks
- TypeScript compilation: PASSED
- All tests: 47 PASSED
- Code coverage: >85% (90.21% for CommandService, 100% for CommandController)
- Linting: PASSED

Fixes #89

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

apps/api/src/federation/federation.module.ts

@@ -11,6 +11,7 @@ import { FederationController } from "./federation.controller";
 import { FederationAuthController } from "./federation-auth.controller";
 import { IdentityLinkingController } from "./identity-linking.controller";
 import { QueryController } from "./query.controller";
+import { CommandController } from "./command.controller";
 import { FederationService } from "./federation.service";
 import { CryptoService } from "./crypto.service";
 import { FederationAuditService } from "./audit.service";
@@ -20,6 +21,7 @@ import { OIDCService } from "./oidc.service";
 import { IdentityLinkingService } from "./identity-linking.service";
 import { IdentityResolutionService } from "./identity-resolution.service";
 import { QueryService } from "./query.service";
+import { CommandService } from "./command.service";
 import { PrismaModule } from "../prisma/prisma.module";
 
 @Module({
@@ -36,6 +38,7 @@ import { PrismaModule } from "../prisma/prisma.module";
     FederationAuthController,
     IdentityLinkingController,
     QueryController,
+    CommandController,
   ],
   providers: [
     FederationService,
@@ -47,6 +50,7 @@ import { PrismaModule } from "../prisma/prisma.module";
     IdentityLinkingService,
     IdentityResolutionService,
     QueryService,
+    CommandService,
   ],
   exports: [
     FederationService,
@@ -57,6 +61,7 @@ import { PrismaModule } from "../prisma/prisma.module";
     IdentityLinkingService,
     IdentityResolutionService,
     QueryService,
+    CommandService,
   ],
 })
 export class FederationModule {}