Delete features (#218)

* Implement company and account deletion features

- Add event types for company and account deletion to CoreEvent.
- Enhance Supabase middleware to handle company context resolution and cookie management for archived companies.
- Create API routes for deleting accounts and companies, including necessary validations and event emissions.
- Implement tests for account and company deletion endpoints to ensure proper functionality and error handling.
- Add retention notice component to inform users about bookkeeping data retention during destructive actions.
- Create database migrations to support soft deletion of companies and anonymization of user accounts, ensuring compliance with retention laws.

* feat: enhance account deletion process and update user notifications

* Add service client for onboarding completion check and update escape hatch visibility

* Enhance invite flow and email handling for company members

* Refactor company context and RLS policies for active company isolation

- Update `switchCompany` to remove unnecessary revalidation as client handles navigation.
- Revise `getActiveCompanyId` to prioritize `user_preferences` and validate against non-archived memberships.
- Modify `setActiveCompany` to ensure `user_preferences` is the authoritative source while maintaining cookie compatibility.
- Enhance middleware to resolve active company using `user_preferences` and fallback to first non-archived membership.
- Introduce new API route `/api/company/current` to fetch the active company ID for cross-tab synchronization.
- Implement `CompanyTabSync` component for real-time active company enforcement across tabs.
- Create migration for RLS policies to enforce single-active-company isolation using `current_active_company_id()`.

* feat: implement viewer role enforcement for write permissions

- Added `useCanWrite` hook to determine if the current user has write permissions based on their role in the active company.
- Updated various components (JournalEntryForm, CustomerForm, DeadlineForm, etc.) to disable write actions and show a lock icon with a tooltip for users without write permissions.
- Introduced `requireWritePermission` function to enforce write permissions at the API level, returning a 403 response for viewers.
- Created tests to verify the behavior of the viewer role and write permissions.
- Added database migration to enforce read-only access for viewers at the database level.

lib/hooks/use-can-write.ts

@@ -0,0 +1,23 @@
+'use client'
+
+import { useCompany } from '@/contexts/CompanyContext'
+
+/**
+ * Returns whether the current user can perform write actions in the
+ * active company. Viewers (role === 'viewer') get `canWrite = false`;
+ * owner / admin / member all get `canWrite = true`. Users with no active
+ * company (null role) also get `canWrite = false`.
+ *
+ * Used by every write-action button (create / edit / delete / send /
+ * approve / etc.) across the dashboard to render the button in a
+ * disabled state with a lock icon and tooltip.
+ *
+ * This is the UI layer of the viewer role enforcement. The API layer
+ * (`requireWritePermission()`) and RLS layer (`current_user_can_write()`)
+ * remain the security-critical backstops — this hook only controls what
+ * the user sees and can click.
+ */
+export function useCanWrite(): { canWrite: boolean } {
+  const { role } = useCompany()
+  return { canWrite: role !== null && role !== 'viewer' }
+}