feat: integrate Stripe payment with subscription plans

Add Stripe payment integration across the project:

- Add @stripe/stripe-js dependency
- Configure Stripe environment variables (secret key, publishable key, webhook secret) for dev, local, and production environments
- Add Product/Price IDs for monthly, quarterly, and annual subscription tiers
- Extend subscription plan data with voiceMinutesPerDay quotas (30/45/60 minutes per tier)
- Update .gitignore to exclude implementation_plan.md

pnpm-lock.yaml

@@ -11,6 +11,9 @@ importers:
       '@fingerprintjs/fingerprintjs':
         specifier: ^5.2.0
         version: 5.2.0
+      '@stripe/stripe-js':
+        specifier: ^9.8.0
+        version: 9.8.0
       '@xstate/react':
         specifier: ^5
         version: 5.0.5(@types/react@19.2.16)(react@19.2.4)(xstate@5.32.0)
@@ -41,6 +44,9 @@ importers:
       react-dom:
         specifier: 19.2.4
         version: 19.2.4(react@19.2.4)
+      stripe:
+        specifier: ^22.2.1
+        version: 22.2.1(@types/node@20.19.41)
       unstorage:
         specifier: ^1.17.5
         version: 1.17.5
@@ -674,6 +680,10 @@ packages:
   '@standard-schema/spec@1.1.0':
     resolution: {integrity: sha512-l2aFy5jALhniG5HgqrD6jXLi/rUWrKvqN/qJx6yoJsgKhblVd+iqqU4RCXavm/jPityDo5TCvKMnpjKnOriy0w==}
 
+  '@stripe/stripe-js@9.8.0':
+    resolution: {integrity: sha512-DHJpol/98VKyojNSYmpkB5vOMnlf87hPe0wPxyaYTNiTMk5QjKMXDfSZLwGctYIXAgAWDFeRABc8lFAj0BELyw==}
+    engines: {node: '>=12.16'}
+
   '@swc/helpers@0.5.15':
     resolution: {integrity: sha512-JQ5TuMi45Owi4/BIMAJBoSQoOJu12oOk/gADqlcUL9JEdHB8vyjUSsxqeNXnmXHjYKMi2WcYtezGEEhqUI/E2g==}
 
@@ -2554,6 +2564,15 @@ packages:
     resolution: {integrity: sha512-6fPc+R4ihwqP6N/aIv2f1gMH8lOVtWQHoqC4yK6oSDVVocumAsfCqjkXnqiYMhmMwS/mEHLp7Vehlt3ql6lEig==}
     engines: {node: '>=8'}
 
+  stripe@22.2.1:
+    resolution: {integrity: sha512-ULAtq25USBEx3yeN5zimEkfYVFETVMP5om25Ryr8ol11P62imaCZLBIEW78T7zm7Wg3wnZi+80S72yf3LCpNhw==}
+    engines: {node: '>=18'}
+    peerDependencies:
+      '@types/node': '>=18'
+    peerDependenciesMeta:
+      '@types/node':
+        optional: true
+
   styled-jsx@5.1.6:
     resolution: {integrity: sha512-qSVyDTeMotdvQYoHWLNGwRFJHC+i+ZvdBRYosOFgC+Wg1vx4frN2/RG/NA7SYqqvKNLf39P2LSRA2pu6n0XYZA==}
     engines: {node: '>= 12.0.0'}
@@ -3439,6 +3458,8 @@ snapshots:
 
   '@standard-schema/spec@1.1.0': {}
 
+  '@stripe/stripe-js@9.8.0': {}
+
   '@swc/helpers@0.5.15':
     dependencies:
       tslib: 2.8.1
@@ -5543,6 +5564,10 @@ snapshots:
 
   strip-json-comments@3.1.1: {}
 
+  stripe@22.2.1(@types/node@20.19.41):
+    optionalDependencies:
+      '@types/node': 20.19.41
+
   styled-jsx@5.1.6(@babel/core@7.29.7)(react@19.2.4):
     dependencies:
       client-only: 0.0.1