fix: prevent trial reset on device rebind

confirmBind and mockBind now check trial history before granting trial.
Previously only checked for active subscriptions — if trial expired,
rebinding would create a new 7-day trial, allowing infinite free usage.
Now checks if user ever had a trial (any status), skips if so.

server/src/dao/binding.dao.js

@@ -95,17 +95,23 @@ async function confirmBind(userId, deviceId, bindToken) {
       'UPDATE bindings SET bind_status = 1, bind_time = NOW() WHERE binding_id = ?',
       [rows[0].binding_id]
     )
-    // Ensure trial subscription
-    const [subs] = await conn.execute(
+    // Grant trial only if user has never had one before
+    const [activeSubs] = await conn.execute(
       'SELECT subscription_id FROM subscriptions WHERE user_id = ? AND status = 1 AND expire_time > NOW() LIMIT 1',
       [userId]
     )
-    if (subs.length === 0) {
+    if (activeSubs.length === 0) {
+      const [trialHistory] = await conn.execute(
+        "SELECT subscription_id FROM subscriptions WHERE user_id = ? AND plan = 'trial' LIMIT 1",
+        [userId]
+      )
+      if (trialHistory.length === 0) {
         await conn.execute(
           "INSERT INTO subscriptions (user_id, plan, status, amount, start_time, expire_time) VALUES (?, 'trial', 1, 0, NOW(), DATE_ADD(NOW(), INTERVAL 7 DAY))",
           [userId]
         )
       }
+    }
     return true
   })
 }
@@ -136,17 +142,23 @@ async function mockBind(userId, deviceId) {
       "INSERT INTO bindings (user_id, device_id, bind_token, bind_expires, bind_status, bind_time) VALUES (?, ?, 'mock', NOW(), 1, NOW())",
       [userId, deviceId]
     )
-    // Ensure trial
-    const [subs] = await conn.execute(
+    // Grant trial only if user has never had one before
+    const [activeSubs] = await conn.execute(
       'SELECT subscription_id FROM subscriptions WHERE user_id = ? AND status = 1 AND expire_time > NOW() LIMIT 1',
       [userId]
     )
-    if (subs.length === 0) {
+    if (activeSubs.length === 0) {
+      const [trialHistory] = await conn.execute(
+        "SELECT subscription_id FROM subscriptions WHERE user_id = ? AND plan = 'trial' LIMIT 1",
+        [userId]
+      )
+      if (trialHistory.length === 0) {
         await conn.execute(
           "INSERT INTO subscriptions (user_id, plan, status, amount, start_time, expire_time) VALUES (?, 'trial', 1, 0, NOW(), DATE_ADD(NOW(), INTERVAL 7 DAY))",
           [userId]
         )
       }
+    }
     return { success: true }
   })
 }