feat(alerts): Benachrichtigungen per E-Mail und Webhook (#012)

SMTP mit STARTTLS fuer Microsoft 365, Webhook mit HMAC-Signatur, taegliche oder
woechentliche Zusammenfassung, Versandprotokoll und Testversand. Keine
Doppelmeldungen dank Pruefung gegen das Protokoll. 134 Tests.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "proxledger",
-  "version": "0.6.0",
+  "version": "0.7.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "proxledger",
-      "version": "0.6.0",
+      "version": "0.7.0",
       "hasInstallScript": true,
       "dependencies": {
         "@node-rs/argon2": "^2.2.1",
@@ -18,12 +18,14 @@
         "bootstrap-icons": "^1.13.1",
         "croner": "^10.0.1",
         "next": "16.3.5",
+        "nodemailer": "^10.0.10",
         "react": "19.2.8",
         "react-dom": "19.2.8",
         "zod": "^4.6.5"
       },
       "devDependencies": {
         "@types/node": "^24.13.5",
+        "@types/nodemailer": "^8.0.2",
         "@types/react": "^19",
         "@types/react-dom": "^19",
         "dotenv": "^17.4.2",
@@ -3203,6 +3205,16 @@
         "undici-types": "~7.18.0"
       }
     },
+    "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/@types/pg": {
       "version": "8.23.1",
       "resolved": "https://registry.npmjs.org/@types/pg/-/pg-8.23.1.tgz",
@@ -7951,6 +7963,15 @@
         "node": ">=18"
       }
     },
+    "node_modules/nodemailer": {
+      "version": "10.0.10",
+      "resolved": "https://registry.npmjs.org/nodemailer/-/nodemailer-10.0.10.tgz",
+      "integrity": "sha512-He9XskOFms62SyAKkLu8CcGcYHAo+BSHSsORI8s4PJH8qZgZY4L4lDfvyN0twvmbpyG+eGrxpyBlskj9d9rJ8A==",
+      "license": "MIT-0",
+      "engines": {
+        "node": ">=20.0.0"
+      }
+    },
     "node_modules/normalize-svg-path": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/normalize-svg-path/-/normalize-svg-path-1.1.0.tgz",