feat: multi-tenant company refactor (GNU-19) (#153)

* feat: multi-tenant company refactor (GNU-19)

Introduce companies table, company_members, and user_preferences to
support multiple companies per user. All data scoping changes from
user_id to company_id across the entire codebase.

Key changes:
- Database migration: new tables, company_id on 40+ tables, backfill,
  RLS rewrite from user_id to company-member-based, updated RPCs
- Types: Company, CompanyMember, CompanyRole, UserPreferences types;
  company_id added to all entity interfaces; companyId on all events
- Engine: all 7 core functions take companyId; storno, period, year-end
  services updated; 16 report generators updated
- Middleware: company context resolution (cookie → prefs → first company)
- API routes: ~120 routes updated with requireCompanyId()
- Frontend: CompanyProvider context, layout/dashboard/onboarding updated
- Extensions: context factory, 9 extensions, all lib files updated
- Tests: 1880 tests passing, all helpers updated with company_id defaults

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add database migrations for multi-tenant company and team system (GNU-19)

Adds company_invitations, company creation RPC, team_members, account
deletion RPC, and teams table refactor migrations. Updates base
multi-tenant migration with cascading FKs and onboarding_step column.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add team types and update core infrastructure for multi-tenancy (GNU-19)

Adds TeamRole, MemberSource, and Team types. Refactors Supabase service
client to be stateless, updates middleware for team-aware routing, extends
CompanyContext with team/role fields, and updates extension service types
to accept companyId.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* refactor: thread company_id through business logic functions (GNU-19)

Replaces user_id scoping with company_id across all lib modules:
bookkeeping, documents, transactions, invoices, reconciliation, tax,
deadlines, and import. Updates corresponding tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* refactor: thread company_id through API routes and extensions (GNU-19)

Updates all existing API routes to extract and pass companyId. Updates
enable-banking and arcim-migration extensions for company-scoped
transaction ingestion and sync.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add company and team management API routes (GNU-19)

Adds CRUD endpoints for company members, company invitations, team
members, and team invitations. Includes invite token utilities, email
templates, and company switch server action.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add team/company UI components, pages, and dashboard updates (GNU-19)

Adds CompanySwitcher, ConsultantEmptyState, Step0RoleChoice, company
members and team management panels. Updates dashboard layout for
team-aware routing, onboarding for multi-step role choice, and auth
callback for team invite acceptance. Ignores supabase/.branches/.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: add null guards for company in import page (GNU-19)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: move appUrl declaration to outer scope in invite route (GNU-19)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: add optional chaining for company.name in members section (GNU-19)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: add optional chaining for second company.name in members section (GNU-19)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: add null guards for company in extension components (GNU-19)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: pass companyId to executeSIEImport in arcim-migration extension (GNU-19)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: update tests to use companyId instead of userId and improve type handling

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

components/deadlines/DeadlineForm.tsx

@@ -25,7 +25,7 @@ import { formatDateISO, DEADLINE_TYPE_LABELS, PRIORITY_LABELS } from '@/lib/cale
 interface DeadlineFormProps {
   open: boolean
   onOpenChange: (open: boolean) => void
-  onSubmit: (data: Omit<Deadline, 'id' | 'user_id' | 'created_at' | 'updated_at'>) => Promise<void>
+  onSubmit: (data: Omit<Deadline, 'id' | 'user_id' | 'company_id' | 'created_at' | 'updated_at'>) => Promise<void>
   onDelete?: (deadline: Partial<Deadline>) => void
   initialData?: Partial<Deadline>
   initialDate?: Date | null

components/deadlines/DeadlineList.tsx

@@ -12,7 +12,7 @@ import { Plus } from 'lucide-react'
 interface DeadlineListProps {
   deadlines: Deadline[]
   customers: { id: string; name: string }[]
-  onDeadlineCreate: (data: Omit<Deadline, 'id' | 'user_id' | 'created_at' | 'updated_at'>) => Promise<void>
+  onDeadlineCreate: (data: Omit<Deadline, 'id' | 'user_id' | 'company_id' | 'created_at' | 'updated_at'>) => Promise<void>
   onDeadlineToggle: (deadline: Deadline) => Promise<void>
   onDeadlineEdit: (deadline: Deadline) => Promise<void>
   onDeadlineDelete: (deadline: Deadline) => Promise<void>
@@ -67,7 +67,7 @@ export function DeadlineList({
     setTypeFilter('all')
   }
 
-  const handleFormSubmit = async (data: Omit<Deadline, 'id' | 'user_id' | 'created_at' | 'updated_at'>) => {
+  const handleFormSubmit = async (data: Omit<Deadline, 'id' | 'user_id' | 'company_id' | 'created_at' | 'updated_at'>) => {
     if (editingDeadline) {
       await onDeadlineEdit({ ...editingDeadline, ...data })
     } else {