fix: use file-based secrets for Stripe API keys (refs #55)

backend/src/core/config/config-loader.ts

@@ -126,6 +126,9 @@ const secretsSchema = z.object({
   auth0_management_client_secret: z.string(),
   google_maps_api_key: z.string(),
   resend_api_key: z.string(),
+  // Stripe secrets (API keys only - price IDs are config, not secrets)
+  stripe_secret_key: z.string(),
+  stripe_webhook_secret: z.string(),
 });
 
 type Config = z.infer<typeof configSchema>;
@@ -140,6 +143,10 @@ export interface AppConfiguration {
   getRedisUrl(): string;
   getAuth0Config(): { domain: string; audience: string; clientSecret: string };
   getAuth0ManagementConfig(): { domain: string; clientId: string; clientSecret: string };
+  getStripeConfig(): {
+    secretKey: string;
+    webhookSecret: string;
+  };
 }
 
 class ConfigurationLoader {
@@ -178,6 +185,8 @@ class ConfigurationLoader {
       'auth0-management-client-secret',
       'google-maps-api-key',
       'resend-api-key',
+      'stripe-secret-key',
+      'stripe-webhook-secret',
     ];
 
     for (const secretFile of secretFiles) {
@@ -240,6 +249,13 @@ class ConfigurationLoader {
           clientSecret: secrets.auth0_management_client_secret,
         };
       },
+
+      getStripeConfig() {
+        return {
+          secretKey: secrets.stripe_secret_key,
+          webhookSecret: secrets.stripe_webhook_secret,
+        };
+      },
     };
 
     // Set RESEND_API_KEY in environment for EmailService

backend/src/features/subscriptions/CLAUDE.md

@@ -45,10 +45,13 @@ Stripe payment integration for subscription tiers and donations.
 ### Webhooks (Public)
 - POST /api/webhooks/stripe - Stripe webhook (signature verified)
 
-## Environment Variables
+## Configuration
 
-- STRIPE_SECRET_KEY
+### Secrets (files via config-loader)
-- STRIPE_WEBHOOK_SECRET
+- `/run/secrets/stripe-secret-key` - Stripe API secret key
+- `/run/secrets/stripe-webhook-secret` - Stripe webhook signing secret
+
+### Environment Variables (docker-compose)
 - STRIPE_PRO_MONTHLY_PRICE_ID
 - STRIPE_PRO_YEARLY_PRICE_ID
 - STRIPE_ENTERPRISE_MONTHLY_PRICE_ID

backend/src/features/subscriptions/README.md

@@ -151,11 +151,18 @@ When user downgrades to a tier with fewer vehicle allowance:
 5. Selections saved to tier_vehicle_selections table
 6. On upgrade, all vehicles become accessible again
 
-## Environment Variables
+## Configuration
 
+### Secrets (loaded from files via config-loader)
+Secrets are loaded from `/run/secrets/` (or `SECRETS_DIR` env var):
+```
+/run/secrets/stripe-secret-key      # Stripe API secret key
+/run/secrets/stripe-webhook-secret  # Stripe webhook signing secret
+```
+
+### Environment Variables (docker-compose)
+Price IDs are not secrets and are configured via environment variables:
 ```
-STRIPE_SECRET_KEY=sk_live_...
-STRIPE_WEBHOOK_SECRET=whsec_...
 STRIPE_PRO_MONTHLY_PRICE_ID=price_...
 STRIPE_PRO_YEARLY_PRICE_ID=price_...
 STRIPE_ENTERPRISE_MONTHLY_PRICE_ID=price_...

backend/src/features/subscriptions/external/stripe/stripe.client.ts

@@ -5,6 +5,7 @@
 
 import Stripe from 'stripe';
 import { logger } from '../../../../core/logging/logger';
+import { appConfig } from '../../../../core/config/config-loader';
 import {
   StripeCustomer,
   StripeSubscription,
@@ -14,18 +15,18 @@ import {
 
 export class StripeClient {
   private stripe: Stripe;
+  private webhookSecret: string;
 
   constructor() {
-    const apiKey = process.env.STRIPE_SECRET_KEY;
+    const stripeConfig = appConfig.getStripeConfig();
-    if (!apiKey) {
-      throw new Error('STRIPE_SECRET_KEY environment variable is required');
-    }
 
-    this.stripe = new Stripe(apiKey, {
+    this.stripe = new Stripe(stripeConfig.secretKey, {
       apiVersion: '2025-12-15.clover',
       typescript: true,
     });
 
+    this.webhookSecret = stripeConfig.webhookSecret;
+
     logger.info('Stripe client initialized');
   }
 
@@ -237,15 +238,10 @@ export class StripeClient {
    */
   constructWebhookEvent(payload: Buffer, signature: string): StripeWebhookEvent {
     try {
-      const webhookSecret = process.env.STRIPE_WEBHOOK_SECRET;
-      if (!webhookSecret) {
-        throw new Error('STRIPE_WEBHOOK_SECRET environment variable is required');
-      }
-
       const event = this.stripe.webhooks.constructEvent(
         payload,
         signature,
-        webhookSecret
+        this.webhookSecret
       );
 
       logger.info('Stripe webhook event verified', { eventId: event.id, type: event.type });