Merge feature/v2-build-modernization: v2.0 KMP/CMP migration + modernization

chore: add editorconfig, fix ktlint formatting, rename Previews.kt

build: make signing conditional in publish script

fix: update catalog for KMP module API changes

build: upgrade Kotlin 2.2.20 + AGP 8.10.0, fix KMP build issues

refactor: platform-abstract commonMain for KMP compatibility

build: restructure andromeda core to KMP source sets

feat: convert andromeda-illustrations to KMP module with ImageVector illustrations

feat: convert andromeda-icons to KMP module with ImageVector icons

build: add KMP/CMP plugin declarations to version catalog

docs: KMP/CMP migration design — Android + iOS multiplatform

feat: Phase 4 — Button redesign, selection controls, Phosphor icons, status bar fix

feat: add Shapes and ContentEmphasis showcase screens to catalog

feat: add complete design token system (Spacing, Elevation, Motion, Opacity)

refactor: remove all Material dependencies from core library