feat: Complete Phase 7.3 Advanced Features

- Enhanced APT stage with advanced features:
  - Package version pinning and holds
  - Custom repository priorities
  - Specific version installation
  - Updated schemas for all new options

- New dependency resolution stage (org.osbuild.apt.depsolve):
  - Advanced dependency solving with conflict resolution
  - Multiple strategies (conservative, aggressive, resolve)
  - Package optimization and dry-run support

- New Docker/OCI image building stage (org.osbuild.docker):
  - Docker and OCI container image creation
  - Flexible configuration for entrypoints, commands, env vars
  - Image export and multi-format support

- New cloud image generation stage (org.osbuild.cloud):
  - Multi-cloud support (AWS, GCP, Azure, OpenStack, DigitalOcean)
  - Cloud-init integration and provider-specific metadata
  - Live ISO and network boot image creation

- New debug and developer tools stage (org.osbuild.debug):
  - Debug logging and manifest validation
  - Performance profiling and dependency tracing
  - Comprehensive debug reports

- Example manifests for all new features:
  - debian-advanced-apt.json - Advanced APT features
  - debian-docker-container.json - Container image building
  - debian-aws-image.json - AWS cloud image
  - debian-live-iso.json - Live ISO creation
  - debian-debug-build.json - Debug mode

- Updated .gitignore with comprehensive artifact patterns
- All tests passing with 292 passed, 198 skipped
- Phase 7.3 marked as completed in todo.txt

debian-forge is now production-ready with advanced features! 🎉

error-tests/missing-packages.json

@@ -0,0 +1,28 @@
+{
+  "version": "2",
+  "pipelines": [
+    {
+      "runner": "org.osbuild.linux",
+      "name": "build",
+      "stages": [
+        {
+          "type": "org.osbuild.debootstrap",
+          "options": {
+            "suite": "trixie",
+            "mirror": "http://deb.debian.org/debian",
+            "arch": "amd64"
+          }
+        },
+        {
+          "type": "org.osbuild.apt",
+          "options": {
+            "packages": [
+              "nonexistent-package-12345",
+              "another-missing-package-67890"
+            ]
+          }
+        }
+      ]
+    }
+  ]
+}