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/app/data/config/ships.toml

@@ -4,10 +4,9 @@
 # content; stats, materials, and production times are placeholders until the
 # recipe and balancing passes.
 #
-# Unlock progression is mostly disabled (unlock_at_station_level = -1) pending
-# the balancing pass. The capital hulls are the exception: battleship is gated
-# to station level 1, and dreadnought (level 2) requires battleship to be
-# unlocked first (unlock_requires) — a demonstration of the prerequisite chain.
+# Unlock gating is defined in unlocks.toml, not here (REQ-LOCK-EXPLICIT): a ship
+# id granted by an unlock group starts locked and is awarded via a defence
+# station drop; ids absent from unlocks.toml (drone, frigate) start unlocked.
 #
 # Size classes:
 #   xs  drone                      1 cell — exactly one 1x1 module
@@ -22,7 +21,6 @@
 
 [[ship]]
 id = "drone"
-unlock_at_station_level = -1
 layout = ["O"]
 default_modules = [{type = "railgun_s", x = 0, y = 0, rotation = "east"}]
 
@@ -49,7 +47,6 @@ sensor_range_m = 150
 # L-shaped weapon modifier, or an afterburner spanning the full center line.
 [[ship]]
 id = "frigate"
-unlock_at_station_level = -1
 layout = [
     "XOX",
     "OOO",
@@ -84,7 +81,6 @@ sensor_range_m = 200
 # mount medium hardware.
 [[ship]]
 id = "destroyer"
-unlock_at_station_level = 0
 layout = [
     "OXOXO",
     "OOOOO",
@@ -120,7 +116,6 @@ sensor_range_m = 220
 # supports; no 3x3 area exists for an l gun.
 [[ship]]
 id = "cruiser"
-unlock_at_station_level = 2
 layout = [
     "XOOX",
     "OOOO",
@@ -158,8 +153,6 @@ sensor_range_m = 250
 # stern leave no 3x3 area for an l gun and no 2x6 area for a drone hangar.
 [[ship]]
 id = "battlecruiser"
-unlock_at_station_level = 4
-unlock_requires = ["cruiser"]
 layout = [
     "OOXXOO",
     "OOOOOO",
@@ -201,8 +194,6 @@ sensor_range_m = 260
 # so no 2x6 drone hangar fits.
 [[ship]]
 id = "battleship"
-unlock_at_station_level = 6
-unlock_requires = ["battlecruiser"]
 layout = [
     "XOOOOX",
     "OOOOOO",
@@ -244,8 +235,6 @@ sensor_range_m = 280
 # stay the only hangar hull. Bow and stern strips hold supports.
 [[ship]]
 id = "dreadnought"
-unlock_at_station_level = 8
-unlock_requires = ["battleship"]
 layout = [
     "XXXOOOOOXXX",
     "OOOXOOOXOOO",
@@ -288,8 +277,6 @@ sensor_range_m = 300
 # the lower decks hold supports and 2x2 point-defense m guns.
 [[ship]]
 id = "carrier"
-unlock_at_station_level = 9
-unlock_requires = ["battleship"]
 layout = [
     "XOOOOOOOOX",
     "OOOOOOOOOO",