web: PRO needs a proven address — email verification gates the studio

A signed-in account is served exactly like a guest until it opens the
verification link: watermarked 2048px export, no saving, no PRO frames,
GPS stamp or HDF. SMTP is declared in .env; with SMTP_HOST unset the link
goes to the container log. Allowlisted admins count as verified.

docker/backend/package-lock.json

@@ -9,11 +9,13 @@
       "version": "1.0.0",
       "dependencies": {
         "better-sqlite3": "^12.11.1",
-        "fastify": "^5.12.5"
+        "fastify": "^5.12.5",
+        "nodemailer": "^7.0.13"
       },
       "devDependencies": {
         "@types/better-sqlite3": "^9.6.0",
         "@types/node": "^22.20.3",
+        "@types/nodemailer": "^8.0.2",
         "tsx": "^4.23.13",
         "typescript": "^5.9.3"
       }
@@ -597,6 +599,16 @@
         "undici-types": "~6.21.0"
       }
     },
+    "node_modules/@types/nodemailer": {
+      "version": "8.0.2",
+      "resolved": "https://registry.npmjs.org/@types/nodemailer/-/nodemailer-8.0.2.tgz",
+      "integrity": "sha512-c7M5ox8p0nEOfbJ2E9Qcmt8/QCu/VzsiAhzBiZbvky2PhKZDHpKB3sQHBM5MEZNkCfBOaS6S9//AGPRTNB7IaA==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*"
+      }
+    },
     "node_modules/abstract-logging": {
       "version": "2.0.1",
       "resolved": "https://registry.npmjs.org/abstract-logging/-/abstract-logging-2.0.1.tgz",
@@ -1178,6 +1190,15 @@
         "node": ">=10"
       }
     },
+    "node_modules/nodemailer": {
+      "version": "7.0.13",
+      "resolved": "https://registry.npmjs.org/nodemailer/-/nodemailer-7.0.13.tgz",
+      "integrity": "sha512-PNDFSJdP+KFgdsG3ZzMXCgquO7I6McjY2vlqILjtJd0hy8wEvtugS9xKRF2NWlPNGxvLCXlTNIae4serI7dinw==",
+      "license": "MIT-0",
+      "engines": {
+        "node": ">=6.0.0"
+      }
+    },
     "node_modules/on-exit-leak-free": {
       "version": "2.1.2",
       "resolved": "https://registry.npmjs.org/on-exit-leak-free/-/on-exit-leak-free-2.1.2.tgz",