fix(billing): compute plan expiry with Jalali months

Server/plugin/support charges used Gregorian Date#setMonth, so 3 months from 1405/06/01 became 1405/09/02. Now add N Jalali months minus one day (1405/08/30).

package-lock.json

@@ -21,6 +21,7 @@
         "bcrypt": "5.1.1",
         "class-transformer": "^0.5.1",
         "class-validator": "^0.14.2",
+        "jalaali-js": "^2.0.1",
         "mysql2": "^3.23.1",
         "passport": "^0.7.0",
         "passport-jwt": "^4.0.1",
@@ -35,6 +36,7 @@
         "@nestjs/testing": "^11.0.1",
         "@types/bcrypt": "5.0.2",
         "@types/express": "^5.0.0",
+        "@types/jalaali-js": "^1.2.0",
         "@types/jest": "^30.0.0",
         "@types/multer": "^2.2.0",
         "@types/node": "^22.0.0",
@@ -3007,6 +3009,13 @@
         "@types/istanbul-lib-report": "*"
       }
     },
+    "node_modules/@types/jalaali-js": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmmirror.com/@types/jalaali-js/-/jalaali-js-1.2.0.tgz",
+      "integrity": "sha512-DRQKjbfFe0/v3siCou9eFzYjDxJItkJpxbU+/CSptvoRqq2/VmTA6y8QvqK/VELKW6xX3qb174nLZlrFV9OT3Q==",
+      "dev": true,
+      "license": "MIT"
+    },
     "node_modules/@types/jest": {
       "version": "30.0.0",
       "resolved": "https://registry.npmmirror.com/@types/jest/-/jest-30.0.0.tgz",
@@ -7058,6 +7067,15 @@
         "@pkgjs/parseargs": "^0.11.0"
       }
     },
+    "node_modules/jalaali-js": {
+      "version": "2.0.1",
+      "resolved": "https://registry.npmmirror.com/jalaali-js/-/jalaali-js-2.0.1.tgz",
+      "integrity": "sha512-qzTmjw6lZ3V4znyNA8ceYoGgFR+CcF+xEfIYZNcK2ZR0mzdMpMZ6iAcdRPvMgxUVdPMh6QLWCANpTcCJow2U+Q==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=20"
+      }
+    },
     "node_modules/jest": {
       "version": "30.4.2",
       "resolved": "https://registry.npmmirror.com/jest/-/jest-30.4.2.tgz",