feat(mails): send supplier document requests over each store's own SMTP

Replaces the mailto: link with a server-side send, so the message carries the
store's signature and logo instead of depending on each workstation's Outlook.

Store record (groups):
- address, phone and logo (data URI, 200 KB cap) feed the mail signature
- per-store SMTP settings: host, port, SSL/STARTTLS, credentials, sender
  address and display name, with an enable switch
- "test connection" button verifies the server without sending anything
- the empty-form literal, previously repeated five times, becomes one constant

Sending:
- nodemailer transport built per store from its own settings
- multipart mail: plain-text alternative plus HTML whose signature embeds the
  logo as an inline CID attachment, which Outlook renders without the remote
  image blocking that a data: URI would hit
- delivery details are HTML-escaped
- Reply-To set to the store address; the row shows a spinner and refuses a
  second click while a send is in flight

Credentials:
- the SMTP password is never returned to the client; a response-layer
  sanitizer strips it from every /api payload and replaces it with a
  smtpPasswordSet flag, covering the ten-plus queries that join full group
  rows into deliveries, orders and user relations
- an empty password field on save keeps the stored one rather than clearing it

Verified end-to-end against a local SMTP server: transport, auth, From/Reply-To,
multipart structure and the inline logo attachment.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FHdE9nEh8zHhQNGpCgrtYe

package-lock.json

@@ -78,6 +78,7 @@
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         "passport": "^0.7.0",
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@@ -111,6 +112,7 @@
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+        "@types/nodemailer": "^8.0.1",
         "@types/passport": "^1.0.16",
         "@types/passport-local": "^1.0.38",
         "@types/react": "^18.3.27",
@@ -3839,6 +3841,16 @@
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       }
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+    "node_modules/@types/nodemailer": {
+      "version": "8.0.1",
+      "resolved": "https://registry.npmjs.org/@types/nodemailer/-/nodemailer-8.0.1.tgz",
+      "integrity": "sha512-PxpaInm8V1JQDd4j0ds5HfvWQk8JupS1C0Picb96QJsrrRDjBH+DlK7L4ZdNSqNULhiZRQHc40nLVShaGxXAMw==",
+      "dev": true,
+      "license": "MIT",
+      "dependencies": {
+        "@types/node": "*"
+      }
+    },
     "node_modules/@types/passport": {
       "version": "1.0.17",
       "resolved": "https://registry.npmjs.org/@types/passport/-/passport-1.0.17.tgz",
@@ -7349,6 +7361,15 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/nodemailer": {
+      "version": "9.0.5",
+      "resolved": "https://registry.npmjs.org/nodemailer/-/nodemailer-9.0.5.tgz",
+      "integrity": "sha512-wvjiKvjczmsN7U/8006JOdXubgBk2XFAbioDMbT+sM7cPs0QrhJTa6KBRX7P5REGGkDcLUz/EarWidb8G8C1jQ==",
+      "license": "MIT-0",
+      "engines": {
+        "node": ">=6.0.0"
+      }
+    },
     "node_modules/normalize-path": {
       "version": "3.0.0",
       "resolved": "https://registry.npmjs.org/normalize-path/-/normalize-path-3.0.0.tgz",