v0.2.0

Added

• User-defined optimization constraints — add custom linear constraints to
  the operational and investment models, either declaratively in the config
  (custom_constraints) or via plugin Julia overlays, editable from a GUI dialog.
• French and Portuguese GUI translations — fr and pt join English,
  Spanish and Japanese, in exact key parity (placeholders and Qt mnemonics
  preserved); the Preferences language list discovers them automatically.
• GPU-accelerated demand inference — XGBoost demand/density prediction runs
  on a CUDA GPU when one is available (auto-detected, large-batch only), with
  CPU fallback and an ESFEX_XGB_DEVICE override (~2.6× on realistic batches).

Changed

• Grid Builder is responsive on country-scale regions — the "Building
  network" pipeline and the Step-1 fetch aggregation (polygon clip + dedup) now
  run on worker threads with live per-stage status and per-phase timings, so the
  Studio no longer freezes; the network build was also de-quadratized.
• Availability profiles — weather-based capacity factors are now the default
  for wind/solar. Queries are de-duplicated per ~11 km location and fetched
  concurrently with retry/backoff, so cost scales with distinct locations, not
  generator count (a full-Japan build dropped from >30 min to ~1 min). A failed
  weather fetch leaves the unit without a profile rather than fabricating a flat
  value; thermal/hydro keep synthetic profiles.
• Project status promoted from alpha to beta.

Fixed

• Grid Builder simplification: O(n²) dead-end bus pruning made linear.
• "Create new system" dialog widened so its window title is no longer clipped.