Fix file names to respect conventions

Important markdown/text files: UPPERCASE.ext
QML module dirs, qml files: PascalCase
Python module dirs, py files, js files: snake_case
Everything else (including icons): hyphen-case

src/qml/Chat/Banners/UnknownDevicesBanner.qml

@@ -9,14 +9,14 @@ Banner {
     color: theme.chat.unknownDevices.background
 
     avatar.visible: false
-    icon.svgName: "unknown_devices_warning"
+    icon.svgName: "unknown-devices-warning"
     labelText: "Unknown devices are present in this encrypted room."
 
     buttonModel: [
         {
             name: "inspect",
             text: qsTr("Inspect"),
-            iconName: "unknown_devices_inspect",
+            iconName: "unknown-devices-inspect",
         }
     ]
 

src/qml/Pages/EditAccount/Profile.qml

@@ -67,7 +67,7 @@ HGridLayout {
                 width: parent.width
 
                 HIcon {
-                    svgName: "upload_avatar"
+                    svgName: "upload-avatar"
                     dimension: 64
                     Layout.alignment: Qt.AlignCenter
                 }

src/qml/UI.qml

@@ -25,7 +25,7 @@ Item {
     HImage {
         id: mainUIBackground
         fillMode: Image.PreserveAspectCrop
-        source: "../images/login_background.jpg"
+        source: "../images/background.jpg"
         sourceSize.width: Screen.width
         sourceSize.height: Screen.height
         anchors.fill: parent