feat(developers): add password-synced provisioning and deployment confirmation flow

Replace random unrecoverable passwords with a confirmation-based flow:
admin approval generates a secure token and sends a ticket reply with a
confirmation link; the developer clicks the link, enters their SilverDESK
password, and all services (Mattermost, Mailcow, Gitea) are provisioned
with that password. Adds password sync endpoint for SilverDESK resets and
updates the post-signup success panel to redirect to SilverDESK login with
the username pre-populated.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

BlazorApp/appsettings.json

@@ -18,5 +18,10 @@
     "BaseUrl": "https://mail.silverlined.uk",
     "ApiKey": "2A21AA-47E4E5-46DD62-A650F0-BC7566"
   },
+  "Gitea": {
+    "BaseUrl": "https://git.silverlabs.uk",
+    "ApiToken": ""
+  },
+  "SiteBaseUrl": "https://silverlabs.uk",
   "AdminApiKey": "aawb2MHblbfmqdhcS7Xp2/ibQOUbUE1BDoqdJOu0bjM="
 }