Settings: fold Users and Organization into the Settings tabs

The left rail is back to the three places you actually go — Garage,
Charging, Settings — and user management moves inside Settings as an
admin-only tab, next to a new Organization tab that used to be a card
buried in the personal settings. Tab order is Personal settings, Users,
Organization, Integrations. /admin redirects to /settings?tab=users so
old links keep working, and ?tab= picks the starting tab in general.

AdminUsers moves from views/ to components/ since it is a panel now, not
a route, and its page header becomes a section header like its
neighbours. The personal panel was split in two around the integrations
markup, which left no gap between the Profile and Privacy cards; it is
one block again.

Creating a user gets an organization picker for superadmins, defaulting
to "no organization" so an org-less account stays a deliberate choice.
Admins see no picker: the server pins their members to their own org
regardless, which users_test.go now covers along with both superadmin
paths.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Web App/web/src/i18n/da.json

@@ -26,7 +26,6 @@
     "garage": "Garage",
     "charging": "Opladning",
     "settings": "Indstillinger",
-    "users": "Brugere",
     "lightMode": "Lys tilstand",
     "darkMode": "Mørk tilstand",
     "signedIn": "Logget ind",
@@ -104,15 +103,15 @@
   },
 
   "admin": {
-    "eyebrow": "Administration",
     "title": "Brugere",
     "subtitleAll": "Konti på tværs af alle organisationer.",
     "subtitleOrg": "Konti i din organisation.",
-    "subtitleOrgsNote": "Organisationer administreres under Indstillinger.",
     "addUser": "Tilføj bruger",
     "colEmail": "E-mail",
     "colName": "Navn",
     "colOrganization": "Organisation",
+    "noOrganization": "— Ingen organisation —",
+    "organizationHint": "Lad feltet stå tomt for at oprette en konto uden organisation.",
     "colRole": "Rolle",
     "colCreated": "Oprettet",
     "you": "(dig)",
@@ -144,7 +143,9 @@
     "subtitle": "Administrer din konto, udseende og dine data.",
     "tabs": {
       "personal": "Personlige indstillinger",
-      "integrations": "Integrationer"
+      "integrations": "Integrationer",
+      "users": "Brugere",
+      "organization": "Organisation"
     },
 
     "account": {