Feature request: make backtrace clickable

When having a backtrace like


when clicking on `SvnRevision::exportInternal` in

```
#6 0x000055c86f1d38a0 in SvnRevision::exportInternal (this=0x7ffcff8a3e40, key=0x55c86f52c758 "/trunk/lang/sk.po", change=0x7f5be7291998, path_from=0x0, rev_from=-1, current=..., rule=..., matchRules=...) at svn.cpp:874
```

that it opens the source file and jumps to the function https://github.com/svn-all-fast-export/svn2git/blob/572a8ba5526063685a597d1d45eb0434559145a2/src/svn.cpp#L704

And when clicking `svn.cpp:874` it goes here https://github.com/svn-all-fast-export/svn2git/blob/572a8ba5526063685a597d1d45eb0434559145a2/src/svn.cpp#L874

The issue names no gdbgui files, tests, or entry points, so start by locating the backtrace or stack-frame rendering code and any existing source-link handling. Reproduce the shown frame and verify that clicking the function name and the file:line reference opens the corresponding source location.

Written by the indexing model from the issue text.