rsync flags: -a, -n, -p, --exclude, --delete

Feature changes across 15 files:

- -a/--archive: enables -c -m -M (no -s, which slows transfers)
- -n/--dry-run: scan + print without connecting or transferring
- -p <port>: custom SSH port (passed as -p to ssh via execvp)
- --exclude <pattern>: glob-based filename filtering in scanner
- --delete: sender collects file manifest; receiver deletes unlisted files

Protocol: added STATUS_MANIFEST, use_delete field in Config wire format.
New utilities: glob_match(), delete_extras() with recursive directory walk.
Scanner: accepts exclude patterns; skips matching entries.
SSH transport: switched from execlp to execvp for dynamic port arg.
Server + multiprocessing: handle STATUS_MANIFEST in both single and
multithreaded receive paths.

Builds clean, all 7 tests pass.

src/shared/utils.c

@@ -1,9 +1,12 @@
 #include "utils.h"
+#include "array_list.h"
 #include "libgen.h"
+#include <dirent.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 void mkdir_r(char *path) {
   char *path_duplicate = malloc(strlen(path) + 1);
@@ -44,6 +47,75 @@ char *str_dup(const char *string) {
   return new_string;
 }
 
+bool glob_match(const char *pattern, const char *str) {
+  while (*pattern) {
+    if (*pattern == '*') {
+      pattern++;
+      while (*str && *str != '/') {
+        if (glob_match(pattern, str))
+          return true;
+        str++;
+      }
+      return glob_match(pattern, str);
+    } else if (*pattern == '?') {
+      if (!*str || *str == '/')
+        return false;
+      pattern++;
+      str++;
+    } else {
+      if (*pattern != *str)
+        return false;
+      pattern++;
+      str++;
+    }
+  }
+  return *str == '\0';
+}
+
+static void delete_extras_walk(const char *abs_path, const char *rel_path,
+                               ArrayList *manifest) {
+  DIR *dir = opendir(abs_path);
+  if (!dir)
+    return;
+  struct dirent *entry;
+  while ((entry = readdir(dir)) != NULL) {
+    if (strcmp(entry->d_name, ".") == 0 || strcmp(entry->d_name, "..") == 0)
+      continue;
+    char *child_abs = path_cat((char *)abs_path, entry->d_name);
+    char *child_rel = path_cat((char *)rel_path, entry->d_name);
+    struct stat st;
+    if (stat(child_abs, &st) != 0) {
+      free(child_abs);
+      free(child_rel);
+      continue;
+    }
+    if (S_ISDIR(st.st_mode)) {
+      delete_extras_walk(child_abs, child_rel, manifest);
+    } else {
+      // Check if relative path is in manifest
+      bool found = false;
+      for (int i = 0; i < manifest->size; i++) {
+        if (strcmp((char *)manifest->items[i], child_rel) == 0) {
+          found = true;
+          break;
+        }
+      }
+      if (!found) {
+        unlink(child_abs);
+        fprintf(stderr, "  Deleted: %s\n", child_rel);
+      }
+    }
+    free(child_abs);
+    free(child_rel);
+  }
+  closedir(dir);
+  rmdir(abs_path);
+}
+
+void delete_extras(const char *dest_root, ArrayList *manifest) {
+  delete_extras_walk(dest_root, "", manifest);
+}
+
 char *path_cat(char *path1, char *path2) {
   if (path1 == NULL || *path1 == '\0')
     return str_dup(path2);