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>

app/api/import/sie/execute/route.ts

@@ -172,6 +172,7 @@ export async function POST(request: Request) {
 
     // Execute the import
     const result = await executeSIEImport(
+      supabase,
       user.id,
       parsed,
       mappings,

app/api/import/sie/mappings/route.ts

@@ -54,7 +54,7 @@ export async function POST(request: Request) {
   }
 
   try {
-    await saveMappings(user.id, mappings)
+    await saveMappings(supabase, user.id, mappings)
     return NextResponse.json({ success: true })
   } catch (error) {
     return NextResponse.json(

app/api/import/sie/parse/route.ts

@@ -53,7 +53,7 @@ export async function POST(request: Request) {
     const content = decodeBuffer(arrayBuffer, encoding)
 
     // Check for duplicate import
-    const duplicate = await checkDuplicateImport(user.id, content)
+    const duplicate = await checkDuplicateImport(supabase, user.id, content)
     if (duplicate) {
       return NextResponse.json({
         error: 'duplicate',