refactor: move vendor info endpoint to tenancy module

MIGRATION:
- Move app/api/v1/vendor/info.py to app/modules/tenancy/routes/api/vendor.py
- Change endpoint path from GET /{vendor_code} to GET /info/{vendor_code}
- Remove catch-all route ordering dependency

TENANCY MODULE SETUP:
- Mark tenancy module as is_self_contained=True
- Add routes/api/vendor.py with vendor_router
- Add exceptions.py with TenancyException hierarchy
- Add placeholder __init__.py files for services, models, schemas

FRONTEND UPDATES:
- Update static/vendor/js/login.js to use new /vendor/info/{vendor_code} path
- Update static/vendor/js/init-alpine.js to use new /vendor/info/{vendor_code} path

The new path is more explicit and eliminates the need for catch-all route
ordering in the vendor router aggregation.

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

static/vendor/js/init-alpine.js

@@ -98,8 +98,8 @@ function data() {
             if (!this.vendorCode) return;
 
             try {
-                // apiClient prepends /api/v1, so /vendor/{code} → /api/v1/vendor/{code}
-                const response = await apiClient.get(`/vendor/${this.vendorCode}`);
+                // apiClient prepends /api/v1, so /vendor/info/{code} → /api/v1/vendor/info/{code}
+                const response = await apiClient.get(`/vendor/info/${this.vendorCode}`);
                 this.vendor = response;
                 vendorLog.debug('Vendor info loaded', this.vendor);
             } catch (error) {

static/vendor/js/login.js

@@ -57,7 +57,7 @@ function vendorLogin() {
             vendorLoginLog.info('Loading vendor information...');
             this.loading = true;
             try {
-                const response = await apiClient.get(`/vendor/${this.vendorCode}`);
+                const response = await apiClient.get(`/vendor/info/${this.vendorCode}`);
                 this.vendor = response;
                 vendorLoginLog.info('Vendor loaded successfully:', {
                     code: this.vendor.code,