Implement config-driven unlock groups so that multiple things can be unlocked at once (including buildings)

bin/app/data/config/modules.toml

@@ -7,10 +7,9 @@
 # Combat stats are placeholders until the arena balancing pass;
 # production_time_seconds values come from the numbers pass.
 #
-# Unlock progression is mostly disabled (unlock_at_station_level = -1) pending
-# the pacing pass. The railguns are the exception: railgun_m is gated to
-# station level 1, and railgun_l requires railgun_m 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
+# module id granted by an unlock group starts locked and is awarded via a
+# defence station drop; ids absent from unlocks.toml (railgun_s) start unlocked.
 #
 # Surface mask footprint ladder — footprints gate which hulls can mount a
 # module, purely through geometry (see ships.toml for the matching hull
@@ -33,7 +32,6 @@
 [[module]]
 id = "railgun_s"
 tooltip = "Small railgun. Fast-firing, short range, low damage; fits any hull."
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "railgun_s_module", amount = 1}]
 production_time_seconds = 1
@@ -49,7 +47,6 @@ attack_rate_hz = 2.0
 [[module]]
 id = "railgun_m"
 tooltip = "Medium railgun. Higher damage at longer range; needs a 2x2 slot."
-unlock_at_station_level = 2
 surface_mask = [
     "OO",
     "OO"]
@@ -67,8 +64,6 @@ attack_rate_hz = 1.5
 [[module]]
 id = "railgun_l"
 tooltip = "Large railgun. Heavy damage at long range; needs a 3x3 slot."
-unlock_at_station_level = 6
-unlock_requires = ["railgun_m"]
 surface_mask = [
     "OOO",
     "OOO",
@@ -90,7 +85,6 @@ attack_rate_hz = 0.8
 [[module]]
 id = "salvager"
 tooltip = "Collects scrap from wrecks and stores it in the ship's cargo hold."
-unlock_at_station_level = -1
 surface_mask = ["O"]
 materials = [{item = "salvager_module", amount = 1}]
 production_time_seconds = 1
@@ -106,7 +100,6 @@ collection_rate_hz = 0.5
 [[module]]
 id = "repair_tool"
 tooltip = "Repairs damaged friendly ships and defence stations within range."
-unlock_at_station_level = 0
 surface_mask = ["O"]
 materials = [{item = "repair_tool_module", amount = 1}]
 production_time_seconds = 1
@@ -125,7 +118,6 @@ repair_range_m = 80
 [[module]]
 id = "afterburner"
 tooltip = "Greatly boosts top speed and forward acceleration."
-unlock_at_station_level = 2
 surface_mask = ["OOO"]
 materials = [{item = "afterburner_module", amount = 1}]
 production_time_seconds = 1
@@ -140,7 +132,6 @@ added_main_acceleration_mpss = 60
 [[module]]
 id = "maneuvering_thrusters"
 tooltip = "Improves top speed and lateral/braking acceleration."
-unlock_at_station_level = 1
 surface_mask = ["OO"]
 materials = [{item = "maneuvering_thrusters_module", amount = 1}]
 production_time_seconds = 1
@@ -158,7 +149,6 @@ added_maneuvering_acceleration_mpss = 10
 [[module]]
 id = "armor_plates"
 tooltip = "Adds a large flat bonus to the ship's hit points."
-unlock_at_station_level = 0
 surface_mask = ["OO"]
 materials = [{item = "armor_plates_module", amount = 1}]
 production_time_seconds = 1
@@ -172,7 +162,6 @@ added_hp = 1200
 [[module]]
 id = "sensor_booster"
 tooltip = "Extends the ship's sensor range."
-unlock_at_station_level = 1
 surface_mask = ["OO"]
 materials = [{item = "sensor_booster_module", amount = 1}]
 production_time_seconds = 1
@@ -189,7 +178,6 @@ added_sensor_range_m = 50
 [[module]]
 id = "weapon_upgrade"
 tooltip = "Increases the damage of all weapons on the ship."
-unlock_at_station_level = 4
 surface_mask = [
     "OO",
     "OX",
@@ -206,7 +194,6 @@ multiplied_damage = 1.2
 [[module]]
 id = "weapon_primer"
 tooltip = "Increases the fire rate of all weapons on the ship."
-unlock_at_station_level = 4
 surface_mask = [
     "OO",
     "OX",
@@ -223,7 +210,6 @@ multiplied_attack_rate_hz = 1.2
 [[module]]
 id = "weapon_stabilizer"
 tooltip = "Extends weapon range at the cost of some fire rate."
-unlock_at_station_level = 3
 surface_mask = [
     "OO",
     "OX",
@@ -247,7 +233,6 @@ multiplied_attack_rate_hz = 0.8
 [[module]]
 id = "drone_bay"
 tooltip = "Drone launch bay (capability not yet implemented)."
-unlock_at_station_level = 5
 surface_mask = [
     "OO",
     "OO"]
@@ -260,7 +245,6 @@ glyph = "Db"
 [[module]]
 id = "drone_hangar"
 tooltip = "Large drone hangar (capability not yet implemented)."
-unlock_at_station_level = 9
 surface_mask = [
     "OOOOOO",
     "OOOOOO"]