feat: make extension system packageable via enriched ExtensionContext

Enrich ExtensionContext with supabase, emit(), settings, storage, log,
and services so extensions can receive everything through dependency
injection instead of importing core modules directly.

- Add context factory and inject context into event handlers via registry
- Move supplier invoice journal entry creation to core event handler
- Add services.ingestTransactions to ExtensionContext for enable-banking
- Create catch-all API route for extension-declared apiRoutes
- Migrate 5 extensions to accept context with dynamic import fallbacks

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

extensions/general/enable-banking/lib/sync.ts

@@ -1,8 +1,16 @@
-import { SupabaseClient } from '@supabase/supabase-js'
+import type { SupabaseClient } from '@supabase/supabase-js'
 import { getTransactions, getAccountBalance } from './api-client'
-import { ingestTransactions, type RawTransaction } from '@/lib/transactions/ingest'
+import { ingestTransactions as defaultIngest } from '@/lib/transactions/ingest'
+import type { RawTransaction, IngestResult } from '@/types'
 import type { StoredAccount } from '../types'
 
+/** Ingest function signature — matches lib/transactions/ingest */
+export type IngestFn = (
+  supabase: SupabaseClient,
+  userId: string,
+  raw: RawTransaction[]
+) => Promise<IngestResult>
+
 export interface SyncResult {
   imported: number
   duplicates: number
@@ -14,6 +22,10 @@ export interface SyncResult {
  *
  * Fetches transactions from the Enable Banking API, converts to RawTransaction
  * format, and delegates to the shared ingestion pipeline.
+ *
+ * @param ingest - Optional ingest function override (defaults to core ingestTransactions).
+ *                 When called from an extension handler with ctx.services.ingestTransactions,
+ *                 pass that function to avoid direct @/lib imports.
  */
 export async function syncAccountTransactions(
   supabase: SupabaseClient,
@@ -21,7 +33,8 @@ export async function syncAccountTransactions(
   connectionId: string,
   account: StoredAccount,
   fromDate: string,
-  toDate: string
+  toDate: string,
+  ingest: IngestFn = defaultIngest
 ): Promise<SyncResult> {
   const bankTransactions = await getTransactions(
     account.uid,
@@ -44,7 +57,7 @@ export async function syncAccountTransactions(
     import_source: 'enable_banking',
   }))
 
-  const ingestResult = await ingestTransactions(supabase, userId, rawTransactions)
+  const ingestResult = await ingest(supabase, userId, rawTransactions)
 
   // Update account balance
   try {