fix: use custom exceptions in onboarding and add tests

- Create onboarding-specific exceptions (OnboardingNotFoundException, etc.)
- Remove HTTPException usage from API endpoints per architecture rules
- Let exceptions propagate to global handler
- Add 12 integration tests for onboarding API endpoints

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/api/v1/vendor/onboarding.py

@@ -13,16 +13,12 @@ Vendor Context: Uses token_vendor_id from JWT token (authenticated vendor API pa
 
 import logging
 
-from fastapi import APIRouter, Depends, HTTPException
+from fastapi import APIRouter, Depends
 from sqlalchemy.orm import Session
 
 from app.api.deps import get_current_vendor_api
 from app.core.database import get_db
-from app.services.onboarding_service import (
-    OnboardingError,
-    OnboardingService,
-    OnboardingStepError,
-)
+from app.services.onboarding_service import OnboardingService
 from models.database.user import User
 from models.schema.onboarding import (
     CompanyProfileRequest,
@@ -96,24 +92,19 @@ def save_company_profile(
     Updates vendor and company records with provided data.
     """
     service = OnboardingService(db)
-
-    try:
-        result = service.complete_company_profile(
-            vendor_id=current_user.token_vendor_id,
-            company_name=request.company_name,
-            brand_name=request.brand_name,
-            description=request.description,
-            contact_email=request.contact_email,
-            contact_phone=request.contact_phone,
-            website=request.website,
-            business_address=request.business_address,
-            tax_number=request.tax_number,
-            default_language=request.default_language,
-            dashboard_language=request.dashboard_language,
-        )
-        return result
-    except OnboardingError as e:
-        raise HTTPException(status_code=400, detail=str(e))
+    return service.complete_company_profile(
+        vendor_id=current_user.token_vendor_id,
+        company_name=request.company_name,
+        brand_name=request.brand_name,
+        description=request.description,
+        contact_email=request.contact_email,
+        contact_phone=request.contact_phone,
+        website=request.website,
+        business_address=request.business_address,
+        tax_number=request.tax_number,
+        default_language=request.default_language,
+        dashboard_language=request.dashboard_language,
+    )
 
 
 # =============================================================================
@@ -151,19 +142,12 @@ def save_letzshop_api(
     Tests connection first, only saves if successful.
     """
     service = OnboardingService(db)
-
-    try:
-        result = service.complete_letzshop_api(
-            vendor_id=current_user.token_vendor_id,
-            api_key=request.api_key,
-            shop_slug=request.shop_slug,
-            letzshop_vendor_id=request.vendor_id,
-        )
-        return result
-    except OnboardingStepError as e:
-        raise HTTPException(status_code=400, detail=str(e))
-    except OnboardingError as e:
-        raise HTTPException(status_code=500, detail=str(e))
+    return service.complete_letzshop_api(
+        vendor_id=current_user.token_vendor_id,
+        api_key=request.api_key,
+        shop_slug=request.shop_slug,
+        letzshop_vendor_id=request.vendor_id,
+    )
 
 
 # =============================================================================
@@ -197,22 +181,15 @@ def save_product_import_config(
     At least one CSV URL must be provided.
     """
     service = OnboardingService(db)
-
-    try:
-        result = service.complete_product_import(
-            vendor_id=current_user.token_vendor_id,
-            csv_url_fr=request.csv_url_fr,
-            csv_url_en=request.csv_url_en,
-            csv_url_de=request.csv_url_de,
-            default_tax_rate=request.default_tax_rate,
-            delivery_method=request.delivery_method,
-            preorder_days=request.preorder_days,
-        )
-        return result
-    except OnboardingStepError as e:
-        raise HTTPException(status_code=400, detail=str(e))
-    except OnboardingError as e:
-        raise HTTPException(status_code=500, detail=str(e))
+    return service.complete_product_import(
+        vendor_id=current_user.token_vendor_id,
+        csv_url_fr=request.csv_url_fr,
+        csv_url_en=request.csv_url_en,
+        csv_url_de=request.csv_url_de,
+        default_tax_rate=request.default_tax_rate,
+        delivery_method=request.delivery_method,
+        preorder_days=request.preorder_days,
+    )
 
 
 # =============================================================================
@@ -232,19 +209,12 @@ def trigger_order_sync(
     Creates a background job that imports orders from Letzshop.
     """
     service = OnboardingService(db)
-
-    try:
-        result = service.trigger_order_sync(
-            vendor_id=current_user.token_vendor_id,
-            user_id=current_user.id,
-            days_back=request.days_back,
-            include_products=request.include_products,
-        )
-        return result
-    except OnboardingStepError as e:
-        raise HTTPException(status_code=400, detail=str(e))
-    except OnboardingError as e:
-        raise HTTPException(status_code=500, detail=str(e))
+    return service.trigger_order_sync(
+        vendor_id=current_user.token_vendor_id,
+        user_id=current_user.id,
+        days_back=request.days_back,
+        include_products=request.include_products,
+    )
 
 
 @router.get(
@@ -281,14 +251,7 @@ def complete_order_sync(
     This also marks the entire onboarding as complete.
     """
     service = OnboardingService(db)
-
-    try:
-        result = service.complete_order_sync(
-            vendor_id=current_user.token_vendor_id,
-            job_id=request.job_id,
-        )
-        return result
-    except OnboardingStepError as e:
-        raise HTTPException(status_code=400, detail=str(e))
-    except OnboardingError as e:
-        raise HTTPException(status_code=500, detail=str(e))
+    return service.complete_order_sync(
+        vendor_id=current_user.token_vendor_id,
+        job_id=request.job_id,
+    )