feat: implement auto-discard feature for excess stock management

inventoryManager.lua

@@ -426,6 +426,23 @@ local function main()
             end
         end,
 
+        -- Task 5b: Auto-discard excess stock
+        function()
+            if #cfg.TRASH_DROPPERS == 0 then
+                while true do sleep(3600) end
+            end
+            sleep(8)  -- let initial scan finish first
+            log.info("DISCARD", "Auto-discard active with %d trash dropper(s)", #cfg.TRASH_DROPPERS)
+            while true do
+                activity.discarding = true
+                state.needsRedraw = true
+                pcall(ops.discardExcess)
+                activity.discarding = false
+                state.needsRedraw = true
+                sleep(cfg.DISCARD_INTERVAL)
+            end
+        end,
+
         -- Task 6: Low-stock alert checker
         function()
             sleep(5)