Fix critical Linux Mint case sensitivity bug in repository detection

lsb_release -is returns "Linuxmint" (lowercase m) not "LinuxMint"
- Fix condition in lib/system.sh Docker installation
- Fix condition in privileged-setup
- Fix condition in lib/privileges.sh

This was preventing UBUNTU_CODENAME detection from working properly.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/privileges.sh

@@ -198,7 +198,7 @@ install_docker() {
     
     # Add Docker repository with proper Ubuntu codename detection for Linux Mint
     local ubuntu_codename
-    if [[ "$(lsb_release -is)" == "LinuxMint" ]]; then
+    if [[ "$(lsb_release -is)" == "Linuxmint" ]]; then
         # Linux Mint provides UBUNTU_CODENAME in /etc/os-release
         if [[ -f /etc/os-release ]]; then
             ubuntu_codename=$(grep '^UBUNTU_CODENAME=' /etc/os-release | cut -d= -f2)

lib/system.sh

@@ -1148,7 +1148,7 @@ install_docker() {
             local ubuntu_codename
             echo "DEBUG: Configuring Docker repository"
             echo "DEBUG: Detected OS: $(lsb_release -is)"
-            if [[ "$(lsb_release -is)" == "LinuxMint" ]]; then
+            if [[ "$(lsb_release -is)" == "Linuxmint" ]]; then
                 echo "DEBUG: Linux Mint detected, checking for UBUNTU_CODENAME"
                 # Linux Mint provides UBUNTU_CODENAME in /etc/os-release
                 if [[ -f /etc/os-release ]]; then