feat: first-run setup wizard for client dropper config

- startup/client.lua now prompts on first run: asks if a dropper
  is next to the computer, and if so, which side it's on
- Saves config to .dropper_config (JSON with dropperSide,
  redstoneSide, enabled)
- Only launches dropperController if dropper is enabled
- dropperController.lua reads .dropper_config for its sides
  instead of hardcoding 'back'
- Delete .client_setup to re-run the setup wizard

startup/client.lua

@@ -2,6 +2,8 @@
 -- Auto-updates from git then launches inventoryClient + dropperController in parallel
 
 local REPO_RAW = "https://git.spatulaa.com/MayaTheShy/Inventory-Manager-CC/raw/branch/main"
+local SETUP_FILE = ".client_setup"     -- marks first-run complete
+local DROPPER_CONFIG = ".dropper_config"
 
 -- Files to download (destination -> repo path)
 local FILES = {
@@ -65,8 +67,103 @@ else
     print(string.format("All %d files up to date.", updated))
 end
 
+-------------------------------------------------
+-- First-run setup
+-------------------------------------------------
+
+local VALID_SIDES = { "top", "bottom", "left", "right", "front", "back" }
+local function isValidSide(s)
+    for _, v in ipairs(VALID_SIDES) do
+        if v == s then return true end
+    end
+    return false
+end
+
+local function firstRunSetup()
+    if fs.exists(SETUP_FILE) then return end
+
+    print("")
+    print("========== First-Run Setup ==========")
+    print("")
+    write("Is there a dropper next to this computer? (y/n): ")
+    local answer = read():lower():sub(1, 1)
+
+    if answer == "y" then
+        -- Ask which side the dropper is on
+        local side
+        while true do
+            print("")
+            print("Valid sides: top, bottom, left, right, front, back")
+            write("Which side is the dropper on? ")
+            side = read():lower():gsub("%s+", "")
+            if isValidSide(side) then
+                break
+            end
+            print("Invalid side. Please try again.")
+        end
+
+        -- Ask which side to pulse redstone from (defaults to same side)
+        print("")
+        write("Redstone output side [" .. side .. "]: ")
+        local rsSide = read():lower():gsub("%s+", "")
+        if rsSide == "" then rsSide = side end
+        if not isValidSide(rsSide) then
+            print("Invalid side, defaulting to " .. side)
+            rsSide = side
+        end
+
+        -- Save dropper config
+        local cfg = textutils.serialiseJSON({
+            dropperSide  = side,
+            redstoneSide = rsSide,
+            enabled      = true,
+        })
+        local f = fs.open(DROPPER_CONFIG, "w")
+        f.write(cfg)
+        f.close()
+        print("")
+        print("Dropper configured: peripheral=" .. side .. ", redstone=" .. rsSide)
+    else
+        -- No dropper - save config with enabled=false
+        local f = fs.open(DROPPER_CONFIG, "w")
+        f.write(textutils.serialiseJSON({ enabled = false }))
+        f.close()
+        print("No dropper configured.")
+    end
+
+    -- Mark setup as complete
+    local f = fs.open(SETUP_FILE, "w")
+    f.write("done")
+    f.close()
+
+    print("")
+    print("Setup complete!")
+    print("(Delete " .. SETUP_FILE .. " to re-run setup)")
+    sleep(2)
+end
+
+firstRunSetup()
+
+-------------------------------------------------
+-- Determine if dropper controller should run
+-------------------------------------------------
+
+local dropperEnabled = false
+if fs.exists(DROPPER_CONFIG) then
+    local f = fs.open(DROPPER_CONFIG, "r")
+    local ok, cfg = pcall(textutils.unserialiseJSON, f.readAll())
+    f.close()
+    if ok and cfg and cfg.enabled then
+        dropperEnabled = true
+    end
+end
+
 print("")
-print("Starting inventoryClient + dropperController...")
+if dropperEnabled then
+    print("Starting inventoryClient + dropperController...")
+else
+    print("Starting inventoryClient (no dropper)...")
+end
 sleep(1)
 
 -- Reboot listener: reboots this computer on remote command
@@ -90,8 +187,12 @@ local function rebootListener()
     end
 end
 
-parallel.waitForAny(
+local tasks = {
     function() shell.run("inventoryClient.lua") end,
-    function() shell.run("dropperController.lua") end,
-    rebootListener
-)
+    rebootListener,
+}
+if dropperEnabled then
+    table.insert(tasks, function() shell.run("dropperController.lua") end)
+end
+
+parallel.waitForAny(table.unpack(tasks))