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'

rust/src/crypto/base64.rs

@@ -0,0 +1,125 @@
+//! RFC 4648 Base64 Encoding and Decoding Engine
+//! 100% Memory-Safe Rust Implementation for SUB-OS
+
+const BASE64_ALPHABET: &[u8; 64] = b"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+
+pub fn base64_encode(input: &[u8], output: &mut [u8]) -> usize {
+    let mut out_idx = 0;
+    let len = input.len();
+    let mut i = 0;
+
+    while i < len {
+        let b0 = input[i] as usize;
+        let b1 = if i + 1 < len { input[i + 1] as usize } else { 0 };
+        let b2 = if i + 2 < len { input[i + 2] as usize } else { 0 };
+
+        let triple = (b0 << 16) | (b1 << 8) | b2;
+
+        if out_idx + 4 > output.len() {
+            break;
+        }
+
+        output[out_idx] = BASE64_ALPHABET[(triple >> 18) & 0x3F];
+        output[out_idx + 1] = BASE64_ALPHABET[(triple >> 12) & 0x3F];
+        output[out_idx + 2] = if i + 1 < len { BASE64_ALPHABET[(triple >> 6) & 0x3F] } else { b'=' };
+        output[out_idx + 3] = if i + 2 < len { BASE64_ALPHABET[triple & 0x3F] } else { b'=' };
+
+        out_idx += 4;
+        i += 3;
+    }
+
+    out_idx
+}
+
+fn decode_char(c: u8) -> Option<u8> {
+    match c {
+        b'A'..=b'Z' => Some(c - b'A'),
+        b'a'..=b'z' => Some(c - b'a' + 26),
+        b'0'..=b'9' => Some(c - b'0' + 52),
+        b'+' => Some(62),
+        b'/' => Some(63),
+        _ => None,
+    }
+}
+
+pub fn base64_decode(input: &[u8], output: &mut [u8]) -> usize {
+    let mut out_idx = 0;
+    let mut chunk = [0u8; 4];
+    let mut chunk_len = 0;
+
+    for &b in input {
+        if b == b'=' || decode_char(b).is_some() {
+            chunk[chunk_len] = b;
+            chunk_len += 1;
+
+            if chunk_len == 4 {
+                let c0 = decode_char(chunk[0]).unwrap_or(0) as usize;
+                let c1 = decode_char(chunk[1]).unwrap_or(0) as usize;
+                let c2 = if chunk[2] == b'=' { 0 } else { decode_char(chunk[2]).unwrap_or(0) as usize };
+                let c3 = if chunk[3] == b'=' { 0 } else { decode_char(chunk[3]).unwrap_or(0) as usize };
+
+                let triple = (c0 << 18) | (c1 << 12) | (c2 << 6) | c3;
+
+                if out_idx < output.len() {
+                    output[out_idx] = ((triple >> 16) & 0xFF) as u8;
+                    out_idx += 1;
+                }
+                if chunk[2] != b'=' && out_idx < output.len() {
+                    output[out_idx] = ((triple >> 8) & 0xFF) as u8;
+                    out_idx += 1;
+                }
+                if chunk[3] != b'=' && out_idx < output.len() {
+                    output[out_idx] = (triple & 0xFF) as u8;
+                    out_idx += 1;
+                }
+
+                chunk_len = 0;
+            }
+        }
+    }
+
+    out_idx
+}
+
+// C-FFI Export
+#[no_mangle]
+pub extern "C" fn rust_base64_encode(
+    in_buf: *const u8,
+    in_len: usize,
+    out_buf: *mut u8,
+    max_out: usize,
+) -> i32 {
+    if in_buf.is_null() || out_buf.is_null() || max_out == 0 {
+        return -1;
+    }
+    unsafe {
+        let input = core::slice::from_raw_parts(in_buf, in_len);
+        let output = core::slice::from_raw_parts_mut(out_buf, max_out);
+        let written = base64_encode(input, output);
+        if written < max_out {
+            *out_buf.add(written) = 0; // Null terminator
+        }
+        written as i32
+    }
+}
+
+#[no_mangle]
+pub extern "C" fn rust_base64_decode(
+    in_buf: *const u8,
+    in_len: usize,
+    out_buf: *mut u8,
+    max_out: usize,
+) -> i32 {
+    if in_buf.is_null() || out_buf.is_null() || max_out == 0 {
+        return -1;
+    }
+    unsafe {
+        let input = core::slice::from_raw_parts(in_buf, in_len);
+        let output = core::slice::from_raw_parts_mut(out_buf, max_out);
+        let written = base64_decode(input, output);
+        if written < max_out {
+            *out_buf.add(written) = 0;
+        }
+        written as i32
+    }
+}

rust/src/crypto/mod.rs

@@ -1,3 +1,4 @@
 pub mod sha3;
 pub mod aes;
+pub mod base64;
 pub use crate::drivers::chacha20;