Add in-game frame performance profiler

[vanlueckn]

Summary

• Add frame-time profiling with averages, p95/max timings, hitch counts, span breakdowns, history graphs, and spike details.
• Expose profiler controls through the F6 diagnostics overlay and F8 console (prof, reset, pause, resume, csv).
• Instrument major app systems and log profiler summaries on run exit, including --frames N runs.
• Refactor loading and startup flow to integrate profiling throughout the application.
• Document profiler usage and commands in the README and add English/German localization.

Testing

• Added and updated console unit tests covering profiler reporting, controls, CSV export, and reset behavior.
• Not run: full test suite and runtime smoke tests.