Implement config-driven unlock groups

Lift unlocking into first-class unlock groups defined in unlocks.toml, so
one defence-station drop can grant a bundle of ships/modules/buildings/
recipes at once (e.g. the salvager module + salvage bay), and buildings
can now be locked at game start and unlocked via a drop.

Config:
- New UnlocksConfig + ConfigLoader::loadUnlocks + validateUnlocks (unknown/
  duplicate/non-assembler grants, unknown requires, empty group all fail load).
- Drop unlock_at_station_level/unlock_requires from ship/module/recipe defs;
  add unlocked_at_start bool to recipes for graph-unreachable base recipes.

Simulation:
- Track awarded groups + per-building unlock state; an item starts unlocked
  iff no group grants it. Rework generateSchematicChoices/applySchematicChoice
  to operate on groups (grant all members at once). Extend state checksum.
- isBuildingUnlocked query; tryPlaceBuilding rejects locked types.

UI:
- Build-menu buttons for locked buildings start hidden, revealed via a new
  UnlockedBuildingsChangedEvent (emitted from GameWorldView's poll loop).
- Schematic choice dialog lists a group's granted items.
- Blueprint placement excludes locked building types (REQ-LOCK-UI-BLUEPRINT).

Data: unlocks.toml (app + test) reproduces the prior per-item gates as
singleton groups and adds salvage_operations (salvager + salvage_bay, lvl 1)
and reprocessing (reprocessing_plant, lvl 2).

Tests: rewrote unlock/config/recipe-schematic/artifact/wave/shipyard tests
for the group model; added UnlockGroupTest. All 443 cases pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y7N59FsLA5e2kuVdqe4Uhc

bin/test/data/config/unlocks.toml

@@ -0,0 +1,21 @@
+# Unlock groups for the test config (REQ-LOCK-EXPLICIT). Mirrors the previous
+# per-item gating: repair_ship, quick_circuit, advanced_circuit start locked and
+# are awarded via defence station drops. exotic_alloy is intentionally NOT here:
+# it stays implicitly gated (its output/inputs are unreachable), so it is never
+# unlocked. premium_circuit uses unlocked_at_start in recipes.toml. Everything
+# else (interceptor, destroyer, salvage_ship, all modules) starts unlocked.
+
+[[unlock]]
+id = "repair_ship"
+station_level = 0
+ships = ["repair_ship"]
+
+[[unlock]]
+id = "quick_circuit"
+station_level = 0
+recipes = ["quick_circuit"]
+
+[[unlock]]
+id = "advanced_circuit"
+station_level = 1
+recipes = ["advanced_circuit"]