Add Debian package and Gitea APT repository support

debian/control, postinst, prerm, postrm — standard dpkg package lifecycle
debian/files/opt/dupfinder/dupfinder-setup.sh — interactive setup:
  checks Docker, detects NVIDIA GPU, prompts for photos/data paths,
  writes docker-compose.override.yml with GPU reservation if present,
  pulls image from registry (builds from source as fallback)
debian/files/usr/local/bin/dupfinder — CLI wrapper:
  setup / start / stop / restart / status / logs / open / update
debian/files/etc/systemd/system/dupfinder.service — systemd unit,
  guards against starting before setup has run
debian/build-deb.sh — builds .deb and uploads to Gitea package registry;
  prints the exact apt sources.list line on success

Install on any Debian/Ubuntu machine:
  echo "deb [trusted=yes] http://192.168.1.64:3000/api/packages/tocmo0nlord/debian bookworm main" \
    | sudo tee /etc/apt/sources.list.d/dupfinder.list
  sudo apt update && sudo apt install dupfinder
  sudo dupfinder setup

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

debian/files/usr/local/bin/dupfinder

@@ -0,0 +1,81 @@
+#!/bin/bash
+# DupFinder CLI wrapper
+CONF_FILE="/etc/dupfinder.conf"
+COMPOSE_DIR="/opt/dupfinder"
+COMPOSE_YML="$COMPOSE_DIR/docker-compose.yml"
+OVERRIDE_YML="$COMPOSE_DIR/docker-compose.override.yml"
+
+[[ -f "$CONF_FILE" ]] && source "$CONF_FILE"
+: "${APP_PORT:=8765}"
+
+_compose() {
+    docker compose -f "$COMPOSE_YML" -f "$OVERRIDE_YML" "$@"
+}
+
+_require_conf() {
+    if [[ ! -f "$CONF_FILE" ]]; then
+        echo "DupFinder is not configured. Run: sudo dupfinder setup"
+        exit 1
+    fi
+}
+
+case "${1:-help}" in
+    setup)
+        exec bash /opt/dupfinder/dupfinder-setup.sh
+        ;;
+    start)
+        _require_conf
+        sudo systemctl start dupfinder.service
+        echo "DupFinder started — http://localhost:$APP_PORT"
+        ;;
+    stop)
+        sudo systemctl stop dupfinder.service
+        echo "DupFinder stopped."
+        ;;
+    restart)
+        _require_conf
+        sudo systemctl restart dupfinder.service
+        echo "DupFinder restarted — http://localhost:$APP_PORT"
+        ;;
+    status)
+        systemctl status dupfinder.service --no-pager
+        ;;
+    logs)
+        _compose logs -f --tail=100
+        ;;
+    open)
+        _require_conf
+        # Wait for service to be ready then open browser
+        for i in $(seq 1 15); do
+            curl -sf "http://localhost:$APP_PORT/" -o /dev/null && break
+            sleep 1
+        done
+        xdg-open "http://localhost:$APP_PORT" 2>/dev/null || \
+        echo "Open in browser: http://localhost:$APP_PORT"
+        ;;
+    update)
+        _require_conf
+        echo "Pulling latest image..."
+        docker pull tocmo0nlord/dupfinder:latest
+        sudo systemctl restart dupfinder.service
+        echo "Updated and restarted."
+        ;;
+    uninstall)
+        echo "To fully remove DupFinder:  sudo apt remove dupfinder"
+        echo "To also remove data:        sudo apt purge dupfinder"
+        ;;
+    help|--help|-h|*)
+        echo "Usage: dupfinder <command>"
+        echo ""
+        echo "Commands:"
+        echo "  setup      Configure photos path, data path, pull image"
+        echo "  start      Start the service"
+        echo "  stop       Stop the service"
+        echo "  restart    Restart the service"
+        echo "  status     Show systemd service status"
+        echo "  logs       Tail container logs"
+        echo "  open       Open in browser"
+        echo "  update     Pull latest image and restart"
+        echo "  uninstall  Show removal instructions"
+        ;;
+esac