Ensure settings.json is always written and update UI to use it (#24)

Updated `src/downloadthread.cpp` to always write `settings.json` if `useSettings` is enabled, ensuring the file exists even if no specific settings are provided.
Updated `src/configure.qml` to read and write `settings.json` for loading/saving configuration on the drive.
Added logic to remove legacy .txt files (camera1.txt, air.txt, etc.) when writing the new JSON format to avoid conflicts.

Analyze config files created on flashed device (#23)

* Analyze config files created on flashed device

Identified .txt files created on the target device during the flashing/configuration process.
The primary logic is in `src/downloadthread.cpp`.
Files identified: `config.txt`, `openhd/camera1.txt`, `openhd/air.txt`, `openhd/ground.txt`, `openhd/debug.txt`, and `openhd/{sbcValue}.txt`.

* Refactor OpenHD config generation to use a single JSON file

Replaced the creation of multiple .txt configuration files (camera1.txt, air.txt, ground.txt, debug.txt, {sbc}.txt) with a single `openhd/settings.json` file.
The JSON file contains keys: "camera", "sbc", "role", and "debug".
Preserved logic for `config.txt` modification and `QOpenHD.conf` copying.

---------

Author: google-labs-jules[bot]

src/configure.qml

@@ -807,42 +807,40 @@ ImButton {
         mode = ""
         qopenhdConfPresent = false
 
-        var airFile = drivePath("air.txt")
-        var groundFile = drivePath("ground.txt")
-        if (imageWriter.fileExists(airFile)) {
+        var settingsJson = imageWriter.readTextFile(drivePath("settings.json"))
+        var settingsObj = {}
+        if (settingsJson && settingsJson.length > 0) {
+            try {
+                settingsObj = JSON.parse(settingsJson)
+            } catch (e) {
+                console.log("[Configure] Error parsing settings.json:", e)
+            }
+        }
+
+        if (settingsObj.role === "air") {
             bootType = "Air"
-        } else if (imageWriter.fileExists(groundFile)) {
+        } else if (settingsObj.role === "ground") {
             bootType = "Ground"
         } else if (settingsMap.bootType && settingsMap.bootType.options && settingsMap.bootType.options.length > 0) {
             bootType = settingsMap.bootType.options[0].id
         }
 
-        // Detect SBC marker
-        if (settingsMap.sbc && settingsMap.sbc.options) {
-            for (var i = 0; i < settingsMap.sbc.options.length; i++) {
-                var opt = settingsMap.sbc.options[i]
-                var optPath = drivePath(opt.file)
-                if (imageWriter.fileExists(optPath)) {
-                    sbc = opt.id
-                    break
-                }
-            }
-            if (!sbc && settingsMap.sbc.options.length > 0) {
-                sbc = settingsMap.sbc.options[0].id
-            }
+        if (settingsObj.sbc) {
+            sbc = settingsObj.sbc
+        } else if (settingsMap.sbc && settingsMap.sbc.options && settingsMap.sbc.options.length > 0) {
+            sbc = settingsMap.sbc.options[0].id
         }
 
-        if (imageWriter.fileExists(drivePath("debug.txt"))) {
+        if (settingsObj.debug) {
             mode = "debug"
             setDebug.checked = true
         } else {
             mode = ""
             setDebug.checked = false
         }
 
-        var cameraValue = imageWriter.readTextFile(drivePath("camera1.txt")).trim()
-        if (cameraValue.length > 0) {
-            setCameraFromValue(cameraValue)
+        if (settingsObj.camera) {
+            setCameraFromValue(settingsObj.camera)
         } else {
             camera = ""
         }
@@ -870,36 +868,44 @@ ImButton {
 
         console.log("[Configure] Writing settings to", openhdRoot)
 
-        var bootFile = bootType === "Air" ? "air.txt" : (bootType === "Ground" ? "ground.txt" : "")
-        if (bootFile) {
-            imageWriter.writeTextFile(drivePath(bootFile), "")
-            var otherBoot = bootType === "Air" ? "ground.txt" : "air.txt"
-            imageWriter.removeFile(drivePath(otherBoot))
+        var settingsObj = {}
+        if (bootType === "Air") {
+            settingsObj.role = "air"
+        } else if (bootType === "Ground") {
+            settingsObj.role = "ground"
         }
 
-        if (settingsMap.sbc && settingsMap.sbc.options) {
-            for (var i = 0; i < settingsMap.sbc.options.length; i++) {
-                var opt = settingsMap.sbc.options[i]
-                var targetPath = drivePath(opt.file)
-                if (opt.id === sbc) {
-                    imageWriter.writeTextFile(targetPath, "")
-                } else {
-                    imageWriter.removeFile(targetPath)
-                }
-            }
+        if (sbc && sbc.length > 0) {
+            settingsObj.sbc = sbc
         }
 
         if (mode === "debug") {
-            imageWriter.writeTextFile(drivePath("debug.txt"), "")
-        } else {
-            imageWriter.removeFile(drivePath("debug.txt"))
+            settingsObj.debug = true
         }
 
         var camValue = cameraValueForSelection()
         if (camValue && camValue.length > 0) {
-            imageWriter.writeTextFile(drivePath("camera1.txt"), camValue)
-        } else {
+            settingsObj.camera = camValue
+        }
+
+        var jsonString = JSON.stringify(settingsObj, null, 4)
+        if (imageWriter.writeTextFile(drivePath("settings.json"), jsonString)) {
+            // Clean up old files if they exist, just in case
+            imageWriter.removeFile(drivePath("air.txt"))
+            imageWriter.removeFile(drivePath("ground.txt"))
+            imageWriter.removeFile(drivePath("debug.txt"))
             imageWriter.removeFile(drivePath("camera1.txt"))
+            // We don't easily know which SBC file might exist, so we might skip cleaning those up
+            // or iterate through sbc options to delete them. For now, assuming fresh flash or JSON usage.
+             if (settingsMap.sbc && settingsMap.sbc.options) {
+                for (var i = 0; i < settingsMap.sbc.options.length; i++) {
+                    var opt = settingsMap.sbc.options[i]
+                    imageWriter.removeFile(drivePath(opt.file))
+                }
+            }
+        } else {
+             onError(qsTr("Failed to write settings.json to the drive."))
+             return
         }
 
         if (qopenhdConfPath && qopenhdConfPath.length > 0) {