feat: rework modules, items and fuel

docs/PRODUCTION.md

@@ -49,7 +49,6 @@ A recipe should conceptually define:
 - cycle time
 - valid producing module types
 - optional workforce requirement
-- optional power or fuel requirement
 
 Recipes should be first-class design objects, not hidden assumptions inside modules.
 
@@ -60,7 +59,6 @@ Recipes are executed by production-capable modules.
 Examples:
 
 - refinery module
-- fuel processing module
 - factory module
 - food-chain module later
 - shipyard support module
@@ -112,16 +110,6 @@ For now:
 
 This keeps the initial system consistent and simple.
 
-## Power Interaction
-
-Production should also respect power and fuel state.
-
-Without power:
-
-- production stops
-
-This is especially important for stations because no-fuel means no-power, and no-power means no normal operation.
-
 ## Input Shortage Behavior
 
 If inputs are missing:
@@ -153,7 +141,6 @@ The exact recipes can evolve, but the intended shape includes chains like:
 
 2. refining or processing
    - ore -> refined goods
-   - gas -> fuel
    - food-loop conversions later
 
 3. industrial use