chore(deps): drop the separate nodemailer types

nodemailer 10 is a TypeScript rewrite and ships its own declarations, so
the hand-added @types/nodemailer package now shadows them with the types
of a release two majors old. The email sender keeps its default import
and its Transporter type from the package itself.

The new floor is Node 20; the image and the engines field are on 22.

package.json

@@ -114,7 +114,6 @@
     "@tailwindcss/postcss": "^4",
     "@testcontainers/postgresql": "^12.1.0",
     "@types/node": "26.1.1",
-    "@types/nodemailer": "^8.0.1",
     "@types/pg": "^8.23.1",
     "@types/qrcode": "^1.5.6",
     "@types/react": "^19",

pnpm-lock.yaml

@@ -210,9 +210,6 @@ importers:
       '@types/node':
         specifier: 26.1.1
         version: 26.1.1
-      '@types/nodemailer':
-        specifier: ^8.0.1
-        version: 8.0.1
       '@types/pg':
         specifier: ^8.23.1
         version: 8.23.1
@@ -2906,9 +2903,6 @@ packages:
   '@types/node@26.1.1':
     resolution: {integrity: sha512-nxAkRSVkN1Y0JC1W8ky/fTfkGsMmcrRsbx+3XoZE+rMOX71kLYTV7fLXpqud1GpbpP5TuffXFqfX7fH2GgZREw==}
 
-  '@types/nodemailer@8.0.1':
-    resolution: {integrity: sha512-PxpaInm8V1JQDd4j0ds5HfvWQk8JupS1C0Picb96QJsrrRDjBH+DlK7L4ZdNSqNULhiZRQHc40nLVShaGxXAMw==}
-
   '@types/pako@2.0.4':
     resolution: {integrity: sha512-VWDCbrLeVXJM9fihYodcLiIv0ku+AlOa/TQ1SvYOaBuyrSKgEcro95LJyIsJ4vSo6BXIxOKxiJAat04CmST9Fw==}
 
@@ -9576,10 +9570,6 @@ snapshots:
     dependencies:
       undici-types: 8.3.0
 
-  '@types/nodemailer@8.0.1':
-    dependencies:
-      '@types/node': 26.1.1
-
   '@types/pako@2.0.4': {}
 
   '@types/pg@8.23.1':