feat: implemented plugin configuration UI and calendar event action slot

- Add configSchema support to plugin manifest and ServerPlugin registry
- Add schema-driven admin config page (string, secret, boolean, number, select fields)
- Add per-plugin config storage backend (JSON files + REST API)
- Add calendar-event-actions and admin-plugin-page slot names to plugin store
- Add registerCalendarEventAction and registerAdminPage to plugin API
- Add calendarFormHooks (onCalendarEventFormOpen/Save) to hook bus
- Add PluginSlot in calendar event modal for plugin action buttons
- Style calendar event action buttons to match Bulwark outline button design
- Add Configure link per plugin in admin plugins dashboard
- Add Jitsi Meet plugin with tests (repos/plugins/jitsi-meet)
- Exclude data/admin/plugins from ESLint (deployed plugin bundles)

components/calendar/event-modal.tsx

@@ -18,6 +18,7 @@ import {
   getStatusCounts,
   buildParticipantMap,
 } from "@/lib/calendar-participants";
+import { PluginSlot } from "@/components/plugins/plugin-slot";
 import { useSettingsStore } from "@/stores/settings-store";
 
 export interface PendingEventPreview {
@@ -810,6 +811,23 @@ export function EventModal({
               placeholder="https://meet.example.com/..."
               maxLength={2000}
             />
+            <PluginSlot
+              name="calendar-event-actions"
+              className="mt-2 flex flex-wrap gap-2"
+              extraProps={{
+                eventData: {
+                  title,
+                  description,
+                  start: startDate + 'T' + startTime,
+                  end: endDate + 'T' + endTime,
+                  isAllDay: allDay,
+                  location,
+                  virtualLocation,
+                  calendarId,
+                },
+                setVirtualLocation,
+              }}
+            />
           </div>
 
           <div>