Move additional files/tests to BitFoundation (#1102)

localPackages/BitFoundation/Sources/BitFoundation/FileTransferLimits.swift

@@ -0,0 +1,23 @@
+/// Centralized thresholds for Bluetooth file transfers to keep payload sizes sane on constrained radios.
+public enum FileTransferLimits {
+    /// Absolute ceiling enforced for any file payload (voice, image, other).
+    public static let maxPayloadBytes: Int = 1 * 1024 * 1024 // 1 MiB
+    /// Voice notes stay small for low-latency relays.
+    public static let maxVoiceNoteBytes: Int = 512 * 1024 // 512 KiB
+    /// Compressed images after downscaling should comfortably fit under this budget.
+    public static let maxImageBytes: Int = 512 * 1024 // 512 KiB
+    /// Worst-case size once TLV metadata and binary packet framing are included for the largest payloads.
+    public static let maxFramedFileBytes: Int = {
+        let maxMetadataBytes = Int(UInt16.max) * 2 // fileName + mimeType TLVs
+        let tlvEnvelopeOverhead = 18 + maxMetadataBytes // TLV tags + lengths + metadata bytes
+        let binaryEnvelopeOverhead = BinaryProtocol.v2HeaderSize
+            + BinaryProtocol.senderIDSize
+            + BinaryProtocol.recipientIDSize
+            + BinaryProtocol.signatureSize
+        return maxPayloadBytes + tlvEnvelopeOverhead + binaryEnvelopeOverhead
+    }()
+
+    public static func isValidPayload(_ size: Int) -> Bool {
+        size <= maxPayloadBytes
+    }
+}