refactor: consolidate extension system to general-only with manifest-driven architecture

- Remove all sector-specific extensions (construction, ecommerce, export,
  hotel, restaurant, tech) — only general-purpose extensions remain
- Move NE-bilaga and SRU export from extensions to core reports (lib/reports/)
- Move moms-box-mapping from extensions/export/shared to lib/vat/
- Replace per-extension API routes with catch-all dispatcher
  (app/api/extensions/ext/[...path]/route.ts)
- Add manifest.json for each extension with metadata, env vars, and deps
- Add api-routes.ts pattern for extension-defined API endpoints
- Add code generation scripts (generate-extension-registry, create-extension)
- Add extensions.config.json for opt-in extension loading
- Add extensions.schema.json for config validation
- Add email service interface with noop default (lib/email/service.ts)
- Add CI workflow (core-build.yml) to verify core builds with zero extensions
- Add migration 045: expand account_type CHECK for untaxed_reserves
- Update CLAUDE.md with comprehensive extension system documentation
- Update all report engines and bookkeeping services for new imports
- Clean up extensions.schema.json to only list existing extensions

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

types/index.ts

@@ -1665,25 +1665,6 @@ export interface CreditNote extends Invoice {
   credited_invoice_id: string
 }
 
-/** CAMT.053 bank statement (placeholder — CAMT parsing not yet implemented) */
-export interface CAMT053Statement {
-  messageId: string
-  statements: unknown[]
-}
-
-/** CAMT.054 payment notification (placeholder — CAMT parsing not yet implemented) */
-export interface CAMT054Notification {
-  messageId: string
-  notifications: unknown[]
-}
-
-/** Security event payload for audit events */
-export interface AuditSecurityEvent {
-  eventType: string
-  description: string
-  metadata: Record<string, unknown>
-}
-
 /** Generic key-value store record for extensions */
 export interface ExtensionDataRecord {
   id: string