Fix Docker sudo error, 99 back navigation, and empty input exit

install.py:
- sudo prefix now determined by euid (== 0 means root) not by OS name
- Previously used 'sudo ' for all Linux — breaks inside Docker where we
  run as root but sudo is not installed
- Single priv variable computed once at top of install_system_packages()

Dockerfile:
- Add python3-venv back to apt installs
- Was removed as 'unused' but install.py uses 'python3 -m venv' to create
  the virtualenv in APP_INSTALL_DIR; missing package caused venv failure

core.py (HackingTool.show_options + HackingToolsCollection.show_options):
- 99 always returns now instead of sys.exit() when parent is None
  Previously: sub-menus with no parent called sys.exit() — since
  interact_menu() never passes parent, pressing 99 in any category
  exited the entire program instead of returning to the main menu
- Empty Enter (blank input) now continues the loop instead of
  defaulting to "99" and triggering exit
  Previously: Prompt default="99" meant pressing Enter without typing
  anything was treated as choosing exit
- "Exit" label on 99 row changed to "Main Menu" since it now returns

Dockerfile

@@ -12,7 +12,7 @@ LABEL org.opencontainers.image.title="hackingtool" \
 # - --no-install-recommends keeps the layer lean
 RUN apt-get update && \
     apt-get install -y --no-install-recommends \
-        git python3-pip curl wget php && \
+        git python3-pip python3-venv curl wget php && \
     rm -rf /var/lib/apt/lists/*
 
 WORKDIR /root/hackingtool

core.py

@@ -113,10 +113,12 @@ class HackingTool:
 
             if self.PROJECT_URL:
                 table.add_row("98", "Open Project Page")
-            table.add_row("99", f"Back to {parent.TITLE if parent else 'Exit'}")
+            table.add_row("99", f"Back to {parent.TITLE if parent else 'Main Menu'}")
             console.print(table)
 
-            raw = Prompt.ask("\n[bold cyan][?] Select an option[/bold cyan]", default="99")
+            raw = Prompt.ask("\n[bold cyan][?] Select an option[/bold cyan]", default="")
+            if not raw.strip():
+                continue
             try:
                 choice = int(raw)
             except ValueError:
@@ -125,9 +127,7 @@ class HackingTool:
                 continue
 
             if choice == 99:
-                if parent is None:
-                    sys.exit()
-                return 99
+                return
             elif choice == 98 and self.PROJECT_URL:
                 self.show_project_page()
             elif 1 <= choice <= len(self.OPTIONS):
@@ -272,10 +272,12 @@ class HackingToolsCollection:
             if incompatible:
                 console.print(f"[dim]({len(incompatible)} tools hidden — not supported on current OS)[/dim]")
 
-            table.add_row("99", f"Back to {parent.TITLE if parent else 'Exit'}")
+            table.add_row("99", f"Back to {parent.TITLE if parent else 'Main Menu'}")
             console.print(table)
 
-            raw = Prompt.ask("\n[bold cyan][?] Choose a tool[/bold cyan]", default="99")
+            raw = Prompt.ask("\n[bold cyan][?] Choose a tool[/bold cyan]", default="")
+            if not raw.strip():
+                continue
             try:
                 choice = int(raw)
             except ValueError:
@@ -283,9 +285,7 @@ class HackingToolsCollection:
                 continue
 
             if choice == 99:
-                if parent is None:
-                    sys.exit()
-                return 99
+                return
             elif choice == 98 and archived:
                 self._show_archived_tools()
             elif 0 <= choice < len(active):

install.py

@@ -107,11 +107,14 @@ def install_system_packages():
         console.print("[warning]Skipping system packages — no package manager found.[/warning]")
         return
 
+    # Use sudo only when not already root (uid != 0).
+    # Inside Docker we run as root and sudo is not installed.
+    priv = "" if os.geteuid() == 0 else "sudo "
+
     # Update index first (skip for brew — not needed)
     if mgr != "brew":
         update_cmd = PACKAGE_UPDATE_CMDS.get(mgr, "")
         if update_cmd:
-            priv = "" if CURRENT_OS.system == "macos" else "sudo "
             console.print(f"[dim]Updating package index ({mgr})...[/dim]")
             subprocess.run(f"{priv}{update_cmd}", shell=True, check=False)
 
@@ -121,7 +124,6 @@ def install_system_packages():
 
     install_tpl = PACKAGE_INSTALL_CMDS[mgr]
     cmd = install_tpl.format(packages=" ".join(packages))
-    priv = "" if CURRENT_OS.system == "macos" else "sudo "
     console.print(f"[dim]Installing system dependencies ({mgr})...[/dim]")
     result = subprocess.run(f"{priv}{cmd}", shell=True, check=False)
     if result.returncode != 0: