feat(ch390): optimize SPI transfer, MAC fallback, and build settings for V1.0.0

- increase UART DMA/ring buffer sizes for mux traffic
- switch SPI1 to Mode0 with prescaler /2 and align CubeMX settings
- refactor CH390 memory read/write path with chunked SPI read and HAL bulk write
- fallback to hardware MAC when configured MAC is invalid (all-zero)
- add mux frame RTT logs and remove redundant UART1 polling
- update Keil post-build viewer integration and include build viewer artifacts
- update AT manual with all-zero MAC behavior

Drivers/CH390/ch390_runtime.c

@@ -157,6 +157,19 @@ struct pbuf *ch390_runtime_input_frame(struct netif *netif)
     return p;
 }
 
+bool ch390_mac_address_valid(const uint8_t *mac)
+{
+    if (mac == NULL) {
+        return false;
+    }
+    for (uint8_t i = 0; i < ETHARP_HWADDR_LEN; ++i) {
+        if (mac[i] == 0u) {
+            return false;
+        }
+    }
+    return true;
+}
+
 void ch390_runtime_init(struct netif *netif, const uint8_t *mac)
 {
     struct ethernetif *ethernetif = (struct ethernetif *)netif->state;
@@ -186,7 +199,19 @@ void ch390_runtime_init(struct netif *netif, const uint8_t *mac)
     SEGGER_RTT_WriteString(0, "ETH init: default\r\n");
     ch390_default_config();
     SEGGER_RTT_WriteString(0, "ETH init: mac\r\n");
-    ch390_set_mac_address((uint8_t *)mac);
+    if (ch390_mac_address_valid(mac)) {
+        ch390_set_mac_address((uint8_t *)mac);
+    }
+    else {
+        if (mac != NULL) {
+            ch390_get_mac((uint8_t *)mac);
+            SEGGER_RTT_printf(0, "ETH init: invalid MAC in config, using hardware MAC: %02X:%02X:%02X:%02X:%02X:%02X\r\n",
+                                  mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
+        }
+        else {
+            SEGGER_RTT_WriteString(0, "ETH init: no MAC in config\r\n");
+        }
+    }
 
     netif->hwaddr_len = ETHARP_HWADDR_LEN;
     SEGGER_RTT_WriteString(0, "ETH init: getmac\r\n");