Rename plugins feature to automations throughout codebase

- Update billing catalog feature codes: can_use_plugins → can_use_automations, can_create_plugins → can_create_automations
- Update all backend permission checks to use new feature codes
- Update API views to return automations permissions to frontend
- Update frontend types and hooks to use automations terminology
- Move Tasks to Extend section in Sidebar alongside Automations
- Update all related tests

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

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

frontend/src/hooks/usePlanFeatures.ts

@@ -83,8 +83,8 @@ export const FEATURE_NAMES: Record<FeatureKey, string> = {
   custom_domain: 'Custom Domain',
   white_label: 'White Label',
   custom_oauth: 'Custom OAuth',
-  plugins: 'Plugins',
-  can_create_plugins: 'Custom Plugin Creation',
+  automations: 'Automations',
+  can_create_automations: 'Custom Automation Creation',
   tasks: 'Scheduled Tasks',
   export_data: 'Data Export',
   video_conferencing: 'Video Conferencing',
@@ -106,9 +106,9 @@ export const FEATURE_DESCRIPTIONS: Record<FeatureKey, string> = {
   custom_domain: 'Use your own custom domain for your booking site',
   white_label: 'Remove SmoothSchedule branding and use your own',
   custom_oauth: 'Configure your own OAuth credentials for social login',
-  plugins: 'Install and use plugins from the marketplace',
-  can_create_plugins: 'Create custom plugins tailored to your business needs',
-  tasks: 'Create scheduled tasks to automate plugin execution',
+  automations: 'Automate repetitive tasks with custom workflows',
+  can_create_automations: 'Create custom automations tailored to your business needs',
+  tasks: 'Create scheduled tasks to automate execution',
   export_data: 'Export your data to CSV or other formats',
   video_conferencing: 'Add video conferencing links to appointments',
   two_factor_auth: 'Require two-factor authentication for enhanced security',