stm32/main: Initialize network before boot.py to fix LAN instantiation.

Move mod_network_init() to run before boot.py instead of after, allowing
network interfaces like network.LAN() to be instantiated in boot.py.

The previous order caused failures when users tried to create network
interfaces in boot.py because the network subsystem wasn't initialized
until after boot.py completed. This change is safe because:

- LWIP is already initialized earlier in main()
- mod_network_init() only initializes the NIC list
- network.country() and network.hostname() still work correctly as
  they just set global variables that are used later

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>
Signed-off-by: Andrew Leech <[email protected]>

Author: pi-anl

ports/stm32/main.c

@@ -589,6 +589,12 @@ void stm32_main(uint32_t reset_mode) {
     // reset config variables; they should be set by boot.py
     MP_STATE_PORT(pyb_config_main) = MP_OBJ_NULL;
 
+    #if MICROPY_PY_NETWORK
+    // Initialize network subsystem before boot.py runs so that network
+    // interfaces can be instantiated in boot.py (LWIP was already initialized earlier)
+    mod_network_init();
+    #endif
+
     // Run optional frozen boot code.
     #ifdef MICROPY_BOARD_FROZEN_BOOT_FILE
     pyexec_frozen_module(MICROPY_BOARD_FROZEN_BOOT_FILE, false);
@@ -626,10 +632,6 @@ void stm32_main(uint32_t reset_mode) {
     servo_init();
     #endif
 
-    #if MICROPY_PY_NETWORK
-    mod_network_init();
-    #endif
-
     // At this point everything is fully configured and initialised.
 
     // Run main.py (or whatever else a board configures at this stage).

ports/stm32/mpnetworkport.c

@@ -32,6 +32,7 @@
 #include "py/runtime.h"
 #include "py/mphal.h"
 #include "shared/netutils/netutils.h"
+#include "eth.h"
 #include "systick.h"
 #include "pendsv.h"
 #include "extmod/modnetwork.h"