feat(quick-260630-gbh-01): account settings page — avatar upload + conditional password form

- AuthUser interface: add isLocalUser? + hasAvatar? fields
- uploadAvatarAction: server action forwarding file to POST /users/me/avatar
- AccountSettingsForm: avatar preview with initial fallback + upload; password form only for local users; LDAP notice
- /settings/general/account page mirroring smtp page structure
- SettingsSidebar: Konto link above SMTP link
- de.json + en.json: categoryAccount + account.* keys

apps/web/src/messages/en.json

@@ -114,7 +114,18 @@
     "categoryWidgets": "Widgets",
     "categoryCalendar": "Calendar",
     "categoryGeneral": "General",
+    "categoryAccount": "Account",
     "categorySmtp": "SMTP",
+    "account": {
+      "title": "Account",
+      "avatarLabel": "Profile Picture",
+      "avatarHelp": "Allowed formats: PNG, JPEG, WebP. Maximum size: 2 MB.",
+      "uploadCta": "Upload picture",
+      "uploadSuccess": "Profile picture updated successfully.",
+      "uploadError": "Upload failed. Please check the file format and size.",
+      "ldapManagedNotice": "Your password is managed via the directory (LDAP) and cannot be changed here.",
+      "passwordSectionTitle": "Change Password"
+    },
     "sourceDeleteConfirm": "Are you sure you want to delete this calendar source?",
     "sourceDeleteCta": "Delete source",
     "providerDeleteConfirm": "Are you sure you want to delete this search provider?",