Add staff permission controls for editing staff and customers

- Add can_edit_staff and can_edit_customers dangerous permissions
- Move Site Builder, Services, Locations, Time Blocks, Payments to Settings permissions
- Link Edit Others' Schedules and Edit Own Schedule permissions
- Add permission checks to StaffViewSet (partial_update, toggle_active, verify_email)
- Add permission checks to CustomerViewSet (update, partial_update, verify_email)
- Fix CustomerViewSet permission key mismatch (can_access_customers)
- Hide Edit/Verify buttons on Staff and Customers pages without permission
- Make dangerous permissions section more visually distinct (darker red)
- Fix StaffDashboard links to use correct paths (/dashboard/my-schedule)
- Disable settings sub-permissions when Access Settings is unchecked

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.idea/smoothschedule.iml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<module version="4">
+  <component name="PyDocumentationSettings">
+    <option name="format" value="PLAIN" />
+    <option name="myDocStringFormat" value="Plain" />
+  </component>
+  <component name="TemplatesService">
+    <option name="TEMPLATE_CONFIGURATION" value="Jinja2" />
+    <option name="TEMPLATE_FOLDERS">
+      <list>
+        <option value="$MODULE_DIR$/smoothschedule/templates" />
+      </list>
+    </option>
+  </component>
+  <component name="TestRunnerService">
+    <option name="PROJECT_TEST_RUNNER" value="py.test" />
+  </component>
+</module>