Remove unused crypto module, DataDir/DefaultDBPath (SQLite remnant),
and ListenAndServe (replaced by direct http.Server in main). Strip 17
unreferenced i18n keys from en/de translations. Add --llm-provider,
--llm-model, and --llm-endpoint CLI flags for runtime LLM override
without a config file. Rewrite README with correct Go 1.25 version,
shields, LLM providers table, Docker/Helm deployment docs. Fix
.gitignore pattern to not match cmd/heatguard/ directory.
