feat(microkernel): implement pure microkernel architecture with vfs_server, net_server, and procmgr

- Added vfs_server in Ring 3 (Endpoint 5) managing unified VFS tree (/, /bin, /etc, /proc, /dev, /tmp)
- Added net_server in Ring 3 (Endpoint 6) owning RTL8139 hardware NIC, DHCP, DNS, and TCP/IPv4 stack
- Refactored procmgr in Ring 3 (Endpoint 4) to handle userspace process spawning via PROC_OP_SPAWN
- Added primitive microkernel syscalls in Ring 0: SYS_TASK_CREATE (29), SYS_TASK_MAP_PAGE (30), SYS_TASK_START (31)
- Updated shell (sh) and desktop GUI (gui_server) to delegate process management and I/O to Ring 3 daemons
- Expanded boot pipeline to orchestrate 7 concurrent Ring 3 servers across dedicated SMP CPU cores

include/abi/net.h

@@ -16,6 +16,12 @@ extern "C" {
 #define ICMP_ECHO_REPLY   0
 #define ICMP_ECHO_REQUEST 8
 
+/* NET_ENDPOINT (6) IPC Opcodes */
+#define NET_OP_GET_CONFIG 1
+#define NET_OP_PING       2
+#define NET_OP_DNS        3
+#define NET_OP_DHCP       4
+
 #pragma pack(push, 1)
 
 typedef struct {