Improve Windows startup and config path handling

[Nordio1]

Summary

This contribution from @mrnordio improves Windows startup compatibility and makes config loading work reliably when Osintgram is launched outside the repository root.

What changed

• prefer pyreadline3 on Windows and keep tab completion optional when readline initialization fails
• add --no-hikerapi to force credentials.ini authentication when a HikerAPI token is configured
• resolve config/credentials.ini and config/settings.json from project-relative paths
• document the new CLI flag in the README and record the fixes in the changelog

Why

The current Windows setup crashes on modern Python because pyreadline==2.1 still expects collections.Callable. The CLI also depends on the shell working directory for credentials.ini and settings.json, which breaks common launch patterns.

Validation

• python .\main.py --help
• python -m compileall .\main.py .\src

Notes

• local config/credentials.ini and config/settings.json changes were intentionally excluded from this PR
• Instagram and HikerAPI authentication flows were not fully exercised because they depend on external credentials and service state