Cleanup: dead code removal, bug fix, and deduplication

[imakris]

Summary

Commit 1: Deduplication, bug fix, and macro cleanup

• Fix bug in NodeGraphicsObject::hoverMoveEvent where | (bitwise OR) was used instead of & (bitwise AND) for testing NodeFlag::Resizable, making the condition always true
• Deduplicate ~80 lines of JSON style macros across NodeStyle, ConnectionStyle, and GraphicsViewStyle by extracting shared readColor/writeColor/readFloat/writeFloat/readBool/writeBool helpers into Style.hpp
• Extract portCountRole() helper into ConnectionIdUtils.hpp to replace repeated ternary expressions across 7 source files
• Extract DataFlowGraphModel::connectDelegateModel() to deduplicate ~30 lines of identical signal connection setup between addNode() and loadNode()
• Remove dead code: unused hash specializations in ConnectionIdHash.hpp, unused NODE_EDITOR_DEMANGLED macro, commented-out code in 4 files, unused PySide2/Shiboken2 cmake modules
• Simplify oppositePort() switch statement

Commit 2: Dead code, unused includes, stale forward declarations

• Remove phantom forward declarations for non-existent classes (NodeDataModel, ConnectionGeometry, GraphModel, NodeGeometry) — leftovers from a previous API version
• Remove dead methods: connectionRequiredPort(), nodePortScenePosition(), connectionEndScenePosition() in NodeConnectionInteraction; addGraphicsEffect() in ConnectionGraphicsObject
• Remove #if 0 blocks in NodeDelegateModelRegistry.hpp (~26 lines of old type converter API)
• Remove unused includes: QUuid (3 headers), QUuidStdHash, iostream, QFile, QMessageBox, QMargins, QIcon, QJsonObject, NodeConnectionInteraction.hpp, NodeState.hpp, ConnectionGraphicsObject.hpp
• Remove duplicate includes: NodeState.hpp in NodeGraphicsObject.hpp, QColor in NodeDelegateModel.hpp
• Remove unused using declarations and variables

Commit 3: Fix broken forwarding header, minor include cleanup

• Fix include/QtNodes/NodeGeometry forwarding header: was pointing to non-existent internal/NodeGeometry.hpp, now correctly points to internal/AbstractNodeGeometry.hpp
• Remove unused QVariant includes from QUuidStdHash.hpp and QStringStdHash.hpp
• Remove unused QObject include from Style.hpp

Commit 4: Structural refactors

• Extract DefaultNodeGeometryBase intermediate class: DefaultHorizontalNodeGeometry and DefaultVerticalNodeGeometry shared ~120 lines of identical code (constructor, boundingRect, size, captionRect, portTextRect, maxPortsTextAdvance, maxPortsExtent, and 4 member variables). These are now in a shared base class.
• Unify pointsC1C2Horizontal/pointsC1C2Vertical into a single computeControlPoints(Qt::Orientation) method — identical structure with X/Y swapped, now parameterized by axis.
• Extract selectedItemsOfType<T> template helper to deduplicate selectedNodes() / selectedGroups() iteration pattern.

Total net reduction: ~960 lines across 45+ files.

Test plan

• Verify all existing unit tests pass
• Verify node resizing correctly checks the Resizable flag (bug fix)
• Verify style loading/saving works correctly with the new shared helpers
• Verify DataFlowGraphModel node creation and loading still connects all delegate signals
• Verify horizontal and vertical node geometry rendering is unchanged
• Verify connection Bezier curves render identically in both orientations
• Verify no compilation regressions from removed includes/forward declarations

https://claude.ai/code/session_015aZAxLSpakeTpF7zaq6D2F