feat: add flexible region matching to servers API

- Add shared buildFlexibleRegionConditions() in utils.ts
- Add COUNTRY_NAME_TO_REGIONS mapping for country/city expansion
- Update servers.ts to use flexible region matching (korea, tokyo, japan, etc.)
- Update recommend.ts to use shared function (remove duplicate code)
- Fix servers GROUP BY to show all regions (it.id, r.id)
- Update CLAUDE.md with single-line curl examples

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

src/handlers/servers.ts

@@ -3,7 +3,7 @@
  */
 
 import type { Env } from '../types';
-import { jsonResponse, isValidServer, DEFAULT_REGION_FILTER_SQL } from '../utils';
+import { jsonResponse, isValidServer, DEFAULT_REGION_FILTER_SQL, buildFlexibleRegionConditions } from '../utils';
 
 /**
  * GET /api/servers - Server list with filtering
@@ -42,9 +42,9 @@ export async function handleGetServers(
         it.instance_family,
         it.gpu_count,
         it.gpu_type,
-        MIN(pr.monthly_price) as monthly_price,
-        MIN(r.region_name) as region_name,
-        MIN(r.region_code) as region_code
+        pr.monthly_price,
+        r.region_name,
+        r.region_code
       FROM instance_types it
       JOIN providers p ON it.provider_id = p.id
       JOIN pricing pr ON pr.instance_type_id = it.id
@@ -79,11 +79,13 @@ export async function handleGetServers(
     }
 
     if (region) {
-      query += ` AND r.region_code = ?`;
-      params.push(region);
+      // Flexible region matching: supports country names, codes, city names
+      const { conditions, params: regionParams } = buildFlexibleRegionConditions([region]);
+      query += ` AND (${conditions.join(' OR ')})`;
+      params.push(...regionParams);
     }
 
-    query += ` GROUP BY it.id ORDER BY MIN(pr.monthly_price) ASC LIMIT 100`;
+    query += ` GROUP BY it.id, r.id ORDER BY pr.monthly_price ASC LIMIT 100`;
 
     const result = await env.DB.prepare(query).bind(...params).all();