feat(admin): web admin panel — user CRUD, role assignment, system health (#150)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/admin/admin-health.controller.ts

@@ -0,0 +1,73 @@
+import { Controller, Get, Inject, UseGuards } from '@nestjs/common';
+import { sql, type Db } from '@mosaic/db';
+import { createQueue } from '@mosaic/queue';
+import { DB } from '../database/database.module.js';
+import { AgentService } from '../agent/agent.service.js';
+import { ProviderService } from '../agent/provider.service.js';
+import { AdminGuard } from './admin.guard.js';
+import type { HealthStatusDto, ServiceStatusDto } from './admin.dto.js';
+
+@Controller('api/admin/health')
+@UseGuards(AdminGuard)
+export class AdminHealthController {
+  constructor(
+    @Inject(DB) private readonly db: Db,
+    @Inject(AgentService) private readonly agentService: AgentService,
+    @Inject(ProviderService) private readonly providerService: ProviderService,
+  ) {}
+
+  @Get()
+  async check(): Promise<HealthStatusDto> {
+    const [database, cache] = await Promise.all([this.checkDatabase(), this.checkCache()]);
+
+    const sessions = this.agentService.listSessions();
+    const providers = this.providerService.listProviders();
+
+    const allOk = database.status === 'ok' && cache.status === 'ok';
+
+    return {
+      status: allOk ? 'ok' : 'degraded',
+      database,
+      cache,
+      agentPool: { activeSessions: sessions.length },
+      providers: providers.map((p) => ({
+        id: p.id,
+        name: p.name,
+        available: p.available,
+        modelCount: p.models.length,
+      })),
+      checkedAt: new Date().toISOString(),
+    };
+  }
+
+  private async checkDatabase(): Promise<ServiceStatusDto> {
+    const start = Date.now();
+    try {
+      await this.db.execute(sql`SELECT 1`);
+      return { status: 'ok', latencyMs: Date.now() - start };
+    } catch (err) {
+      return {
+        status: 'error',
+        latencyMs: Date.now() - start,
+        error: err instanceof Error ? err.message : String(err),
+      };
+    }
+  }
+
+  private async checkCache(): Promise<ServiceStatusDto> {
+    const start = Date.now();
+    const handle = createQueue();
+    try {
+      await handle.redis.ping();
+      return { status: 'ok', latencyMs: Date.now() - start };
+    } catch (err) {
+      return {
+        status: 'error',
+        latencyMs: Date.now() - start,
+        error: err instanceof Error ? err.message : String(err),
+      };
+    } finally {
+      await handle.close().catch(() => {});
+    }
+  }
+}