Add Ubuntu 25.04 compatibility fixes, LLVM 18 GHDL build, and installer corrections

[sonivishal66666]

This pull request ports eSim to Ubuntu 25.04 (Plucky Puffin) and fixes multiple installer, dependency, and toolchain failures introduced by the new OS stack.

Summary of work:

• Enabled Ubuntu 25.04 support in the installer (forward-compatible OS mapping)
• Fixed broken APT calls and removed invalid KiCad PPAs
• Added PPA cleanup logic to prevent permanent APT breakage
• Corrected KiCad library extraction and symbol paths
• Fixed NGHDL extraction and deprecated libcanberra dependency
• Implemented LLVM 18 toolchain side-loading to build GHDL on LLVM 20 systems
• Corrected invalid GHDL configure flags
• Fixed desktop launcher paths
• Added Python virtual environment support to satisfy PEP 668 (Python 3.13)
• Added full forensic bug report and failure/validation screenshots under BUG_REPORT/

This PR includes:

• 13 distinct bug fixes
• All changes isolated to Ubuntu-specific installers and runtime
• No changes to Fedora or Windows trees

The full technical analysis, root cause breakdown, and reproduction evidence is available in:
BUG_REPORT/Bug_Report/Bug_Report.md