feat(billing): add subscription and Stripe billing router

- Add stripeCustomerId column to users table
- Create Stripe client initialization (web/src/server/stripe.ts)
- Add billing service with getOrCreateCustomer, checkout/portal sessions,
  subscription management, invoice listing, and webhook event handling
- Create billing tRPC router with getSubscription, createCheckoutSession,
  createPortalSession, cancelSubscription, reactivateSubscription, listInvoices
- Add raw webhook endpoint at /api/stripe/webhook with signature verification
- Define Valibot schemas for all billing procedure inputs
- Wire billing router into root tRPC router
- Update schema tests for new column/index counts
- Write unit tests for billing service and router

pnpm-lock.yaml

@@ -67,6 +67,9 @@ importers:
       solid-js:
         specifier: ^1.9.5
         version: 1.9.13
+      stripe:
+        specifier: ^22.1.1
+        version: 22.1.1(@types/node@25.9.1)
       tailwindcss:
         specifier: ^4.0.0
         version: 4.3.0
@@ -3130,6 +3133,15 @@ packages:
   strip-literal@3.1.0:
     resolution: {integrity: sha512-8r3mkIM/2+PpjHoOtiAW8Rg3jJLHaV7xPwG+YRGrv6FP0wwk/toTpATxWYOW0BKdWwl82VT2tFYi5DlROa0Mxg==}
 
+  stripe@22.1.1:
+    resolution: {integrity: sha512-cmodIYP27tBkJ8G7DuGgWw0PFuemlFZbuF3Wwr1TrjFjUa3T7NIgCe6TVwX8BO2ynu+xtTuDGfHafNDCPt9lXA==}
+    engines: {node: '>=18'}
+    peerDependencies:
+      '@types/node': '>=18'
+    peerDependenciesMeta:
+      '@types/node':
+        optional: true
+
   supports-color@10.2.2:
     resolution: {integrity: sha512-SS+jx45GF1QjgEXQx4NJZV9ImqmO2NPz5FNsIHrsDjh2YsHnawpan7SNQ1o8NuhrbHZy9AZhIoCUiCeaW/C80g==}
     engines: {node: '>=18'}
@@ -6431,6 +6443,10 @@ snapshots:
     dependencies:
       js-tokens: 9.0.1
 
+  stripe@22.1.1(@types/node@25.9.1):
+    optionalDependencies:
+      '@types/node': 25.9.1
+
   supports-color@10.2.2: {}
 
   supports-color@7.2.0: