feat: vCPU 및 대역폭 기반 서버 필터링 추가

- minVcpu: expected_users / vcpu_per_users 기반 최소 vCPU 필터링
- 대역폭 기반 provider 필터링:
  - very_heavy (>6TB/month): Linode만 표시
  - heavy (2-6TB/month): Linode 우선 정렬
- queryCandidateServers에 minVcpu, bandwidthEstimate 파라미터 추가

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

src/index.ts

@@ -720,8 +720,26 @@ async function handleRecommend(
       ? Math.max(...memoryIntensiveSpecs.map(s => s.min_memory_mb))
       : undefined;
 
-    // Phase 2: Query candidate servers (depends on minMemoryMb)
-    const candidates = await queryCandidateServers(env.DB, body, minMemoryMb, lang);
+    // Calculate minimum vCPU based on expected users and tech specs
+    // Formula: expected_users / vcpu_per_users (use minimum ratio from all tech specs)
+    let minVcpu: number | undefined;
+    if (techSpecs.length > 0) {
+      const vcpuRequirements = techSpecs.map(spec => {
+        // Use vcpu_per_users: 1 vCPU can handle N users
+        // So for expected_users, we need: expected_users / vcpu_per_users vCPUs
+        const vcpuNeeded = Math.ceil(body.expected_users / spec.vcpu_per_users);
+        return vcpuNeeded;
+      });
+      minVcpu = Math.max(...vcpuRequirements, 1); // At least 1 vCPU
+      console.log(`[Recommend] Minimum vCPU required: ${minVcpu} (for ${body.expected_users} users)`);
+    }
+
+    // Calculate bandwidth estimate for provider filtering
+    const bandwidthEstimate = estimateBandwidth(body.expected_users, body.use_case, body.traffic_pattern);
+    console.log(`[Recommend] Bandwidth estimate: ${bandwidthEstimate.monthly_tb >= 1 ? bandwidthEstimate.monthly_tb + ' TB' : bandwidthEstimate.monthly_gb + ' GB'}/month (${bandwidthEstimate.category})`);
+
+    // Phase 2: Query candidate servers (depends on minMemoryMb, minVcpu, bandwidth)
+    const candidates = await queryCandidateServers(env.DB, body, minMemoryMb, minVcpu, bandwidthEstimate, lang);
     console.log('[Recommend] Candidate servers:', candidates.length);
 
     if (candidates.length === 0) {
@@ -904,12 +922,16 @@ function escapeLikePattern(pattern: string): string {
 /**
  * Query candidate servers from database
  * @param minMemoryMb - Minimum memory requirement from tech specs (optional)
+ * @param minVcpu - Minimum vCPU requirement based on expected users (optional)
+ * @param bandwidthEstimate - Bandwidth estimate for provider prioritization (optional)
  * @param lang - Language for currency selection: 'ko' → KRW, others → retail USD
  */
 async function queryCandidateServers(
   db: D1Database,
   req: RecommendRequest,
   minMemoryMb?: number,
+  minVcpu?: number,
+  bandwidthEstimate?: BandwidthEstimate,
   lang: string = 'en'
 ): Promise<Server[]> {
   // Select price column based on language
@@ -961,6 +983,28 @@ async function queryCandidateServers(
     console.log(`[Candidates] Filtering by minimum memory: ${minMemoryMb}MB (${(minMemoryMb/1024).toFixed(1)}GB)`);
   }
 
+  // Filter by minimum vCPU requirement (from expected users + tech specs)
+  if (minVcpu && minVcpu > 0) {
+    query += ` AND it.vcpu >= ?`;
+    params.push(minVcpu);
+    console.log(`[Candidates] Filtering by minimum vCPU: ${minVcpu}`);
+  }
+
+  // Provider filtering based on bandwidth requirements
+  // Heavy bandwidth (>2TB/month) → Linode only (better bandwidth allowance)
+  // Very heavy bandwidth (>6TB/month) → Linode only with warning
+  if (bandwidthEstimate) {
+    if (bandwidthEstimate.category === 'very_heavy') {
+      // >6TB/month: Linode only (includes up to 20TB depending on plan)
+      query += ` AND p.id = 1`; // Linode only
+      console.log(`[Candidates] Very heavy bandwidth (${bandwidthEstimate.monthly_tb}TB/month): Linode only`);
+    } else if (bandwidthEstimate.category === 'heavy') {
+      // 2-6TB/month: Prefer Linode, but allow Vultr
+      // Order by Linode first (handled in ORDER BY)
+      console.log(`[Candidates] Heavy bandwidth (${bandwidthEstimate.monthly_tb}TB/month): Linode preferred`);
+    }
+  }
+
   // Country name to code mapping for common names
   // Note: Use specific city names to avoid LIKE pattern collisions (e.g., 'de' matches 'Delhi')
   const countryNameToCode: Record<string, string[]> = {
@@ -1035,7 +1079,11 @@ async function queryCandidateServers(
   }
 
   // Group by instance + region to show each server per region
-  query += ` GROUP BY it.id, r.id ORDER BY monthly_price ASC LIMIT 50`;
+  // For heavy bandwidth, prioritize Linode (p.id=1) over Vultr (p.id=2)
+  const orderByClause = bandwidthEstimate?.category === 'heavy'
+    ? `ORDER BY CASE WHEN p.id = 1 THEN 0 ELSE 1 END, monthly_price ASC`
+    : `ORDER BY monthly_price ASC`;
+  query += ` GROUP BY it.id, r.id ${orderByClause} LIMIT 50`;
 
   const result = await db.prepare(query).bind(...params).all();