v2.0-beta

app: rewrite landing page to explain the .sql vs .eso load flow

Replaces the outdated "make sure Output:SQLite is in your IDF" instruction with
the v2 model: load an existing eplusout.sql directly, or load the raw eplusout.eso
and Timestep converts it (no re-run). Adds a note that originals are never
modified (ESO conversions are cached separately, not written next to the model).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>