Add Stripe billing integration + update free tier to 100 PDFs/mo

package-lock.json

@@ -13,7 +13,8 @@
         "helmet": "^8.0.0",
         "marked": "^15.0.0",
         "nanoid": "^5.0.0",
-        "puppeteer": "^24.0.0"
+        "puppeteer": "^24.0.0",
+        "stripe": "^20.3.1"
       },
       "devDependencies": {
         "@types/express": "^5.0.0",
@@ -3377,6 +3378,23 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/stripe": {
+      "version": "20.3.1",
+      "resolved": "https://registry.npmjs.org/stripe/-/stripe-20.3.1.tgz",
+      "integrity": "sha512-k990yOT5G5rhX3XluRPw5Y8RLdJDW4dzQ29wWT66piHrbnM2KyamJ1dKgPsw4HzGHRWjDiSSdcI2WdxQUPV3aQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=16"
+      },
+      "peerDependencies": {
+        "@types/node": ">=16"
+      },
+      "peerDependenciesMeta": {
+        "@types/node": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/tar-fs": {
       "version": "3.1.1",
       "resolved": "https://registry.npmjs.org/tar-fs/-/tar-fs-3.1.1.tgz",