feat: Global-Admin Org-Switcher fuer info@aegis-sight.de

Ermoeglicht dem Global Admin (is_global_admin Flag) zwischen
Organisationen zu wechseln. Neue Endpoints: GET /api/auth/organizations,
POST /api/auth/switch-org. Org-Dropdown im Header-Menue, nur fuer
Global Admin sichtbar. Komplett herausnehmbar (Flag + Code-Bloecke).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/auth.py

@@ -20,6 +20,7 @@ def create_token(
     role: str = "member",
     tenant_id: int = None,
     org_slug: str = None,
+    is_global_admin: bool = False,
 ) -> str:
     """JWT-Token erstellen mit Tenant-Kontext."""
     now = datetime.now(TIMEZONE)
@@ -31,6 +32,7 @@ def create_token(
         "role": role,
         "tenant_id": tenant_id,
         "org_slug": org_slug,
+        "is_global_admin": is_global_admin,
         "iss": JWT_ISSUER,
         "aud": JWT_AUDIENCE,
         "iat": now,
@@ -69,6 +71,7 @@ async def get_current_user(
         "role": payload.get("role", "member"),
         "tenant_id": payload.get("tenant_id"),
         "org_slug": payload.get("org_slug"),
+        "is_global_admin": payload.get("is_global_admin", False),
     }