Refactor clear_all resets and file-local helper layout

[trailcode]

Summary

• Extend clear_all for enums and aggregates; convert multi-field reset sites across shape, sketch, and GUI.
• Align anonymous-namespace helpers with trailing _ names, top forward decls, and bottom definitions (GUI, shape/sketch, utl_*, main).
• Document the convention in docs/ezycad_code_style.md and clear_all coverage in src/doc/utility.md.
• DRY ImGui add-primitive numeric rows via table_row_input_double_.

Closes #244

Test plan

• Release build of EzyCad / EzyCad_tests
• Full CTest Release (127/127)
• Spot-check add-primitive dialogs and a few tools that use clear_all resets (move/rotate/extrude/cyl-align)

Notes

• Script-console bindings (scr_*.cpp) left alone on purpose.
• Explicit AIS Remove/Erase-then-Nullify sequences unchanged where order matters.

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Note

Low Risk
Refactor and style alignment with no intentional behavior change; clear_all on enums/aggregates is the main semantic extension and is covered by existing tests per the PR test plan.

Overview
clear_all now value-initializes enums and aggregates (in addition to handles via Nullify, optionals, containers, etc.), with docs updated in utility.md and utl.h/utl.inl. Many multi-field reset sites in GUI, OCCT view, and shape/sketch tools (move, rotate, extrude, cyl_align, cross-section, dims, underlay, …) are consolidated to clear_all(...) instead of hand-written Nullify() / per-field clears. Shp_cyl_align::reset() delegates to begin(); Shp_rotate gains clear_rotation_vis_() for AIS cleanup.

Code organization follows the documented reader-first / helpers-at-bottom pattern: anonymous-namespace helpers get trailing _ names, forward declarations at the top, definitions at the bottom (gui.cpp log helpers, gui_settings.cpp ImGui JSON/UI, gui_occt_view.cpp STEP import and grid helpers, utl_cad_file_info.cpp, main.cpp CLI parse, and similar across shp_* / skt_* / utl_*). docs/ezycad_code_style.md spells out that convention for private methods and file-local helpers.

gui_add.cpp replaces repeated ImGui table rows with table_row_input_double_ for all add-primitive dialogs. Minor formatting-only tweaks elsewhere (gui.h alignment, planar-face brace cleanup).

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