feat: major UI overhaul — multi-doc assembly workflow, preview enhancements, zoom controls

Before google

fix(manual_assembly): bind click events to inner frame too

fix(manual_assembly): scroll and selection

fix(manual_assembly): dynamic row height for left tree, fix scroll binding

refactor: migrate modules to src/, add logging system, add assembly workshop

refactor: Complete ESKD archive system - rewrite append_document, fix typos, enhance UL generator, add date masking, and improve PDF preview engine

fix: Restore init_cache() function

chore: Add __pycache__/ to .gitignore

refactor: Remove __pycache__ from git tracking

refactor: migrate modules to src/, add logging system, add assembly workshop

refactor: Complete ESKD archive system - rewrite append_document, fix typos, enhance UL generator, add date masking, and improve PDF preview engine

fix: Restore init_cache() function

chore: Add __pycache__/ to .gitignore

refactor: Remove __pycache__ from git tracking

Fix critical issues:

Initial commit: PDM/СЭД система для ЕСКД