fix: install.sh installs git, curl, python3 if missing

- Checks for git before clone/pull — installs via apt/dnf/apk
- Checks for curl before downloading release binary
- Checks for python3 before parsing release JSON
- Multi-distro support (apt-get, dnf, apk)

install.sh

@@ -105,6 +105,42 @@ echo "  ║       ReceiptNext Installer           ║"
 echo "  ╚═══════════════════════════════════════╝"
 echo ""
 
+# ── Install dependencies ───────────────────────────────────────────
+if ! command -v git &>/dev/null; then
+    info "Installing git..."
+    if command -v apt-get &>/dev/null; then
+        sudo_if apt-get update -qq && sudo_if apt-get install -y -qq git 2>&1 | tail -1
+    elif command -v dnf &>/dev/null; then
+        sudo_if dnf install -y git 2>&1 | tail -1
+    elif command -v apk &>/dev/null; then
+        sudo_if apk add git 2>&1 | tail -1
+    else
+        err "Please install git manually, then re-run install.sh"
+        exit 1
+    fi
+fi
+if ! command -v curl &>/dev/null; then
+    info "Installing curl..."
+    if command -v apt-get &>/dev/null; then
+        sudo_if apt-get install -y -qq curl 2>&1 | tail -1
+    elif command -v dnf &>/dev/null; then
+        sudo_if dnf install -y curl 2>&1 | tail -1
+    elif command -v apk &>/dev/null; then
+        sudo_if apk add curl 2>&1 | tail -1
+    fi
+fi
+# python3 is used for parsing release JSON
+if ! command -v python3 &>/dev/null; then
+    info "Installing python3..."
+    if command -v apt-get &>/dev/null; then
+        sudo_if apt-get install -y -qq python3 2>&1 | tail -1
+    elif command -v dnf &>/dev/null; then
+        sudo_if dnf install -y python3 2>&1 | tail -1
+    elif command -v apk &>/dev/null; then
+        sudo_if apk add python3 2>&1 | tail -1
+    fi
+fi
+
 # ── 1. Clone repo ────────────────────────────────────────────────
 if [ -d "$INSTALL_DIR" ]; then
     warn "$INSTALL_DIR already exists — pulling latest..."