feat(backend): add @bytelyst/backend-flags + backend-telemetry, fix config defaults

- Add @bytelyst/backend-flags and @bytelyst/backend-telemetry packages
- Create feature-flags.ts and telemetry.ts wrappers using shared packages
- Add TELEMETRY_ENABLED and FEATURE_FLAGS_ENABLED config fields
- Default DB_PROVIDER to memory (fixes test failures without env vars)
- Add JWT_SECRET dev default and PLATFORM_SERVICE_URL
- 176/176 tests pass

backend/package-lock.json

@@ -11,6 +11,8 @@
         "@azure/cosmos": "^4.2.0",
         "@bytelyst/auth": "file:../../learning_ai_common_plat/packages/auth",
         "@bytelyst/backend-config": "file:../../learning_ai_common_plat/packages/backend-config",
+        "@bytelyst/backend-flags": "file:../../learning_ai_common_plat/packages/backend-flags",
+        "@bytelyst/backend-telemetry": "file:../../learning_ai_common_plat/packages/backend-telemetry",
         "@bytelyst/config": "file:../../learning_ai_common_plat/packages/config",
         "@bytelyst/cosmos": "file:../../learning_ai_common_plat/packages/cosmos",
         "@bytelyst/datastore": "file:../../learning_ai_common_plat/packages/datastore",
@@ -50,6 +52,22 @@
         "vitest": "^3.0.5"
       }
     },
+    "../../learning_ai_common_plat/packages/backend-flags": {
+      "name": "@bytelyst/backend-flags",
+      "version": "0.1.0",
+      "devDependencies": {
+        "typescript": "^5.7.3",
+        "vitest": "^3.0.5"
+      }
+    },
+    "../../learning_ai_common_plat/packages/backend-telemetry": {
+      "name": "@bytelyst/backend-telemetry",
+      "version": "0.1.0",
+      "devDependencies": {
+        "typescript": "^5.7.3",
+        "vitest": "^3.0.5"
+      }
+    },
     "../../learning_ai_common_plat/packages/config": {
       "name": "@bytelyst/config",
       "version": "0.1.0",
@@ -375,6 +393,14 @@
       "resolved": "../../learning_ai_common_plat/packages/backend-config",
       "link": true
     },
+    "node_modules/@bytelyst/backend-flags": {
+      "resolved": "../../learning_ai_common_plat/packages/backend-flags",
+      "link": true
+    },
+    "node_modules/@bytelyst/backend-telemetry": {
+      "resolved": "../../learning_ai_common_plat/packages/backend-telemetry",
+      "link": true
+    },
     "node_modules/@bytelyst/config": {
       "resolved": "../../learning_ai_common_plat/packages/config",
       "link": true

backend/package.json

@@ -18,6 +18,8 @@
     "@bytelyst/cosmos": "file:../../learning_ai_common_plat/packages/cosmos",
     "@bytelyst/datastore": "file:../../learning_ai_common_plat/packages/datastore",
     "@bytelyst/backend-config": "file:../../learning_ai_common_plat/packages/backend-config",
+    "@bytelyst/backend-flags": "file:../../learning_ai_common_plat/packages/backend-flags",
+    "@bytelyst/backend-telemetry": "file:../../learning_ai_common_plat/packages/backend-telemetry",
     "@bytelyst/errors": "file:../../learning_ai_common_plat/packages/errors",
     "@bytelyst/fastify-auth": "file:../../learning_ai_common_plat/packages/fastify-auth",
     "@bytelyst/fastify-core": "file:../../learning_ai_common_plat/packages/fastify-core",

backend/src/lib/config.ts

@@ -1,11 +1,14 @@
+import { z } from 'zod';
 import { baseBackendConfigSchema } from '@bytelyst/backend-config';
 
 const envSchema = baseBackendConfigSchema.extend({
   PORT: baseBackendConfigSchema.shape.PORT.default(4011),
   SERVICE_NAME: baseBackendConfigSchema.shape.SERVICE_NAME.default('chronomind-backend'),
-}).refine(
-  data => data.DB_PROVIDER === 'memory' || (data.COSMOS_ENDPOINT.length > 0 && data.COSMOS_KEY.length > 0),
-  { message: 'COSMOS_ENDPOINT and COSMOS_KEY are required when DB_PROVIDER is cosmos' }
-);
+  DB_PROVIDER: baseBackendConfigSchema.shape.DB_PROVIDER.default('memory'),
+  JWT_SECRET: z.string().default('dev-secret-do-not-use-in-prod'),
+  PLATFORM_SERVICE_URL: z.string().default('http://localhost:4003'),
+  TELEMETRY_ENABLED: z.coerce.boolean().default(false),
+  FEATURE_FLAGS_ENABLED: z.coerce.boolean().default(false),
+});
 
 export const config = envSchema.parse(process.env);

backend/src/lib/feature-flags.ts

@@ -0,0 +1,15 @@
+import { createFlagRegistry } from '@bytelyst/backend-flags';
+import { config } from './config.js';
+
+const registry = createFlagRegistry({
+  defaults: {
+    'timers.cascade': true,
+    'timers.linked': true,
+    'routines.enabled': true,
+    'households.enabled': true,
+    'shared_timers.enabled': true,
+  },
+  enabled: config.FEATURE_FLAGS_ENABLED,
+});
+
+export const { isFeatureEnabled, getAllFlags, setFlag } = registry;

backend/src/lib/telemetry.ts

@@ -0,0 +1,8 @@
+import { createTelemetryBuffer } from '@bytelyst/backend-telemetry';
+import { config } from './config.js';
+
+export type { TelemetryEvent } from '@bytelyst/backend-telemetry';
+
+const buffer = createTelemetryBuffer({ enabled: config.TELEMETRY_ENABLED });
+
+export const { trackEvent, getBufferedEvents, flushEvents } = buffer;