feat: initial NFC Attendance Hub implementation

- Multi-tenant client management with unique API keys
- Semaphore SMS integration (per-client key + sender name + credit balance)
- DB-based SMS queue with 3-attempt retry and exponential backoff
- Failed SMS dashboard with manual retry button
- Reports page with date/client filter and CSV export
- Admin auth via NextAuth (email/password)
- Docker Compose setup (app + PostgreSQL 16)
- Prisma 5 schema with SmsQueue, SmsLog, Client, User models

Tech: Next.js 14 App Router + TypeScript + Tailwind CSS + Prisma + PostgreSQL

lib/semaphore.ts

@@ -0,0 +1,58 @@
+import axios from 'axios'
+
+const SEMAPHORE_API_URL = 'https://api.semaphore.co/api/v4'
+
+export interface SemaphoreResponse {
+  success: boolean
+  messageId?: string
+  error?: string
+}
+
+export async function sendSms(
+  apiKey: string,
+  senderName: string,
+  phone: string,
+  message: string
+): Promise<SemaphoreResponse> {
+  try {
+    const response = await axios.post(
+      `${SEMAPHORE_API_URL}/messages`,
+      {
+        apikey: apiKey,
+        number: phone,
+        message,
+        sendername: senderName,
+      },
+      { timeout: 15000 }
+    )
+
+    const data = response.data
+    if (Array.isArray(data) && data.length > 0) {
+      const msg = data[0]
+      if (msg.status === 'Queued' || msg.status === 'Sent') {
+        return { success: true, messageId: String(msg.message_id) }
+      }
+      return { success: false, error: msg.status || 'Unknown status' }
+    }
+    return { success: false, error: 'Empty response from Semaphore' }
+  } catch (err: any) {
+    const errorMsg =
+      err.response?.data?.message ||
+      err.response?.data ||
+      err.message ||
+      'SMS send failed'
+    return { success: false, error: String(errorMsg) }
+  }
+}
+
+export async function getBalance(apiKey: string): Promise<number | null> {
+  try {
+    const response = await axios.get(`${SEMAPHORE_API_URL}/account`, {
+      params: { apikey: apiKey },
+      timeout: 10000,
+    })
+    return response.data?.credit_balance ?? null
+  } catch {
+    return null
+  }
+}