fix(security): address medium findings for ACL, limits, and UX

Tighten approve-endpoint to active shares with TTL sessions, reject non-file
FDs, lower default ticket/approval/size caps, show endpoint IDs and Public-mode
warnings, harden Android receive path checks, and run cargo-audit in CI.

shared/src/commonMain/composeResources/values/strings.xml

@@ -22,6 +22,7 @@
     <string name="send_access_approval_description">You approve or refuse every new receiver.</string>
     <string name="send_access_anyone">Anyone with this transfer</string>
     <string name="send_access_anyone_description">No approval is required. Only use this for files you are comfortable sharing.</string>
+    <string name="send_access_anyone_warning">Anyone who has the ticket can download until you stop the share. Do not use this for private or sensitive files.</string>
     <string name="send_file_size_unknown">Size unavailable</string>
     <string name="send_transfer_created">Transfer created.</string>
     <string name="send_transfer_details_title">Transfer details</string>
@@ -173,6 +174,7 @@
     <string name="value_on">On</string>
     <string name="value_off">Off</string>
     <string name="approval_connection_request">Connection request</string>
+    <string name="approval_endpoint_id">Endpoint ID: %1$s</string>
     <string name="approval_pending_count">%1$d requests are waiting</string>
     <string name="core_status_ready">Ready</string>
     <string name="event_log_title">Event log</string>

shared/src/commonMain/kotlin/com/vnidrop/app/feature/approvals/ApprovalCoordinator.kt

@@ -27,6 +27,8 @@ data class PendingApproval(
 	val transferName: String,
 	val receiverName: String?,
 	val receiverDeviceName: String?,
+	/** Cryptographic peer identity from the Iroh connection — not display-name spoofable. */
+	val remoteEndpointId: String,
 	val requestedAt: Long,
 )
 
@@ -162,6 +164,7 @@ private fun ReceiverRequestModel.toPending(): PendingApproval = PendingApproval(
 	transferName = transferName,
 	receiverName = receiverName,
 	receiverDeviceName = receiverDeviceName,
+	remoteEndpointId = remoteEndpointId,
 	requestedAt = requestedAt,
 )
 

shared/src/commonMain/kotlin/com/vnidrop/app/feature/approvals/ApprovalModalHost.kt

@@ -31,6 +31,7 @@ import com.vnidrop.app.ui.theme.LocalVniDropColors
 import org.jetbrains.compose.resources.stringResource
 import vnidrop.shared.generated.resources.Res
 import vnidrop.shared.generated.resources.approval_connection_request
+import vnidrop.shared.generated.resources.approval_endpoint_id
 import vnidrop.shared.generated.resources.approval_pending_count
 import vnidrop.shared.generated.resources.button_approve
 import vnidrop.shared.generated.resources.button_refuse
@@ -78,6 +79,12 @@ fun ApprovalModalHost(
 					style = MaterialTheme.typography.bodyLarge,
 					color = colors.foregroundLight,
 				)
+				// Trusted identity is the endpoint id; display names are peer-provided.
+				Text(
+					stringResource(Res.string.approval_endpoint_id, request.remoteEndpointId),
+					style = MaterialTheme.typography.bodySmall,
+					color = colors.foregroundLighter,
+				)
 				if (state.pending.size > 1) {
 					Text(
 						stringResource(Res.string.approval_pending_count, state.pending.size),

shared/src/commonMain/kotlin/com/vnidrop/app/feature/send/TransferComposer.kt

@@ -51,6 +51,7 @@ import vnidrop.shared.generated.resources.field_sender_name
 import vnidrop.shared.generated.resources.field_transfer_name
 import vnidrop.shared.generated.resources.send_access_anyone
 import vnidrop.shared.generated.resources.send_access_anyone_description
+import vnidrop.shared.generated.resources.send_access_anyone_warning
 import vnidrop.shared.generated.resources.send_access_approval
 import vnidrop.shared.generated.resources.send_access_approval_description
 import vnidrop.shared.generated.resources.send_access_title
@@ -166,6 +167,13 @@ private fun ReviewFileStep(
 		selected = state.accessPolicy == ShareAccessPolicy.AnyoneWithTransfer,
 		onClick = { onAccessPolicyChanged(ShareAccessPolicy.AnyoneWithTransfer) },
 	)
+	if (state.accessPolicy == ShareAccessPolicy.AnyoneWithTransfer) {
+		Text(
+			stringResource(Res.string.send_access_anyone_warning),
+			color = LocalVniDropColors.current.destructiveDefault,
+			style = MaterialTheme.typography.bodySmall,
+		)
+	}
 	if (windowClass == WindowClass.Phone) {
 		Column(verticalArrangement = Arrangement.spacedBy(8.dp)) {
 			ShareButton(state, coreInitialized, onCreateShare, Modifier.fillMaxWidth())