feat: 支持手动切换采集帧率

在 Android、Web 及 Flutter 控制端新增帧率选择 UI，被控端按屏幕刷新率生成支持的帧率档位并上报，允许在保持分辨率不变的情况下仅切换帧率。

另附带更新信号服务器的数据库配置。

webrtc_controller_ios/web_rtc_controller_ios/Control/ControlMessage.swift

@@ -34,6 +34,8 @@ struct ControlMessage {
     var height: Int32 = 0           // field 13, varint
     var fps: Int32 = 0              // field 14, varint
     var streamMode: Int32 = 0       // field 15, varint (0=WebRTC 1=自编码)
+    /// 被控端支持的帧率档位列表（REPORT_RESOLUTION 上报，按屏幕刷新率筛选，升序）。
+    var supportedFps: [Int32] = []  // field 16, repeated varint (packed)
 
     // MARK: - Encode
 
@@ -54,6 +56,16 @@ struct ControlMessage {
         w.writeVarintField(13, UInt64(bitPattern: Int64(height)))
         w.writeVarintField(14, UInt64(bitPattern: Int64(fps)))
         w.writeVarintField(15, UInt64(bitPattern: Int64(streamMode)))
+        // repeated int32 supported_fps = 16（packed 编码）；空列表不编码
+        if !supportedFps.isEmpty {
+            var payload = ProtoWriter()
+            for v in supportedFps {
+                payload.writeVarint(UInt64(bitPattern: Int64(v)))
+            }
+            w.writeVarint(UInt64(16 << 3 | 2))
+            w.writeVarint(UInt64(payload.data.count))
+            w.data.append(payload.data)
+        }
         return w.data
     }
 
@@ -81,6 +93,19 @@ struct ControlMessage {
             case (13, 0): guard let v = r.readVarint() else { return nil }; msg.height = Int32(truncatingIfNeeded: Int64(bitPattern: v))
             case (14, 0): guard let v = r.readVarint() else { return nil }; msg.fps = Int32(truncatingIfNeeded: Int64(bitPattern: v))
             case (15, 0): guard let v = r.readVarint() else { return nil }; msg.streamMode = Int32(truncatingIfNeeded: Int64(bitPattern: v))
+            case (16, 2):
+                // packed repeated int32：先读长度，再在区间内逐个读 varint
+                guard let len = r.readVarint() else { return nil }
+                let end = r.offset + Int(len)
+                guard end <= data.endIndex else { return nil }
+                while r.offset < end {
+                    guard let v = r.readVarint() else { return nil }
+                    msg.supportedFps.append(Int32(truncatingIfNeeded: Int64(bitPattern: v)))
+                }
+            case (16, 0):
+                // 兼容非 packed 编码（逐项 varint）
+                guard let v = r.readVarint() else { return nil }
+                msg.supportedFps.append(Int32(truncatingIfNeeded: Int64(bitPattern: v)))
             default:
                 // 未知字段按 wire type 跳过
                 if !r.skip(wireType: wire) { return nil }