Add admin panel, enhanced search, Gonher import and expand API

- Add admin interface (admin.html, admin.js) for managing catalog data
- Add enhanced search module with advanced filtering capabilities
- Expand server.py with new API endpoints and admin functionality
- Add Gonher catalog import scripts (import_gonher_catalog.py, import_gonher_complete.py)
- Add demo data population script and sample CSV data
- Update customer landing page and dashboard with UI improvements
- Update database with enriched vehicle and parts data

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

dashboard/sample_data/manufacturers_sample.csv

@@ -0,0 +1,16 @@
+name,type,quality_tier,country,website
+Brembo,aftermarket,premium,Italy,https://www.brembo.com
+Bosch,aftermarket,premium,Germany,https://www.bosch.com
+Denso,aftermarket,premium,Japan,https://www.denso.com
+ACDelco,aftermarket,standard,USA,https://www.acdelco.com
+Raybestos,aftermarket,standard,USA,https://www.raybestos.com
+Wagner,aftermarket,standard,USA,https://www.wagnerbrake.com
+Monroe,aftermarket,standard,USA,https://www.monroe.com
+KYB,aftermarket,premium,Japan,https://www.kyb.com
+NGK,aftermarket,premium,Japan,https://www.ngk.com
+Aisin,aftermarket,premium,Japan,https://www.aisin.com
+Gates,aftermarket,premium,USA,https://www.gates.com
+Continental,aftermarket,premium,Germany,https://www.continental.com
+Moog,aftermarket,standard,USA,https://www.moogparts.com
+Dorman,aftermarket,economy,USA,https://www.dormanproducts.com
+Centric,aftermarket,standard,USA,https://www.centricparts.com