fix: improve form accessibility with proper label associations

Added missing htmlFor attributes to labels and corresponding IDs to form elements throughout the web UI to enhance accessibility. This ensures screen readers can correctly identify form controls and improves browser autofill functionality. Changes include:

- Fixed label associations in login form
- Added proper IDs to form elements in Settings component
- Replaced decorative labels with semantic headings in PropertiesView
- Added screen reader accessible labels in RetrievalTesting
- Improved checkbox accessibility in QuerySettings

lightrag_webui/src/features/RetrievalTesting.tsx

@@ -147,13 +147,19 @@ export default function RetrievalTesting() {
             <EraserIcon />
             {t('retrievePanel.retrieval.clear')}
           </Button>
-          <Input
-            className="flex-1"
-            value={inputValue}
-            onChange={(e) => setInputValue(e.target.value)}
-            placeholder={t('retrievePanel.retrieval.placeholder')}
-            disabled={isLoading}
-          />
+          <div className="flex-1 relative">
+            <label htmlFor="query-input" className="sr-only">
+              {t('retrievePanel.retrieval.placeholder')}
+            </label>
+            <Input
+              id="query-input"
+              className="w-full"
+              value={inputValue}
+              onChange={(e) => setInputValue(e.target.value)}
+              placeholder={t('retrievePanel.retrieval.placeholder')}
+              disabled={isLoading}
+            />
+          </div>
           <Button type="submit" variant="default" disabled={isLoading} size="sm">
             <SendIcon />
             {t('retrievePanel.retrieval.send')}