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/static/dashboard.html

@@ -52,6 +52,12 @@
                             <span class="header-dropdown-label">Organisation</span>
                             <span class="header-dropdown-value" id="header-org-name">-</span>
                         </div>
+                        <!-- Global Admin: Org-Switcher (herausnehmbar) -->
+                        <div id="org-switcher-section" class="org-switcher-section" style="display: none;">
+                            <div class="credits-divider"></div>
+                            <label class="org-switcher-label" for="org-switcher-select">Wechseln zu:</label>
+                            <select id="org-switcher-select" class="org-switcher-select"></select>
+                        </div>
                         <div class="header-dropdown-row">
                             <span class="header-dropdown-label">Lizenz</span>
                             <span class="header-dropdown-value" id="header-license-info">-</span>