feat: Add Rust Base64 codec, Process hierarchy (pstree, kill), and VFS visual tree/find applets

- Implement memory-safe RFC-4648 Base64 encoder and decoder in rust/src/crypto/base64.rs
- Add process parent hierarchy tracking (ppid, pgid), task_find_by_pid, task_kill, and task_dump_pstree in kernel/task.c
- Add list_for_each_entry macro in include/lib/list.h
- Add LazyBox applets: 'base64', 'pstree', 'kill', 'tree', 'find', and 'traceroute'

include/kernel/rust.h

@@ -76,6 +76,8 @@ int rust_chacha20_crypt(const uint8_t* key, const uint8_t* nonce, uint32_t count
 int rust_csprng_get_random(uint8_t* buffer, size_t len);
 int rust_sha3_256(const uint8_t* data, size_t len, uint8_t* out);
 int rust_aes128_ecb_encrypt(const uint8_t* key, uint8_t* block);
+int rust_base64_encode(const uint8_t* in_buf, size_t in_len, uint8_t* out_buf, size_t max_out);
+int rust_base64_decode(const uint8_t* in_buf, size_t in_len, uint8_t* out_buf, size_t max_out);
 int rust_crypto_run_benchmark(rust_crypto_bench_result_t* out_result);
 
 // Hardware & Drivers

include/kernel/task.h

@@ -15,6 +15,8 @@ typedef enum {
 
 typedef struct task_struct {
     pid_t pid;
+    pid_t ppid;
+    pid_t pgid;
     char name[32];
     task_state_t state;
     uint64_t rsp;
@@ -23,14 +25,21 @@ typedef struct task_struct {
     uint64_t sleep_until_ticks;
     int priority;
     int time_slice;
+    int exit_code;
     struct list_head list;
+    struct list_head all_list;
 } task_t;
 
 typedef void (*task_entry_fn_t)(void* arg);
 
+void task_init_idle(void);
 task_t* task_create(const char* name, task_entry_fn_t entry, void* arg, int priority);
 void task_exit(int exit_code);
 task_t* task_current(void);
 pid_t task_get_pid(void);
+void task_set_current(task_t* task);
+task_t* task_find_by_pid(pid_t pid);
+int task_kill(pid_t pid, int sig);
+void task_dump_pstree(void);
 
 #endif // _KERNEL_TASK_H

include/lib/list.h

@@ -53,4 +53,9 @@ static inline int list_empty(const struct list_head *head) {
     for (pos = (head)->next, n = pos->next; pos != (head); \
         pos = n, n = pos->next)
 
+#define list_for_each_entry(pos, head, member) \
+    for (pos = list_entry((head)->next, typeof(*pos), member); \
+         &pos->member != (head); \
+         pos = list_entry(pos->member.next, typeof(*pos), member))
+
 #endif // _LIB_LIST_H