Fix SpotBugs SBSC_USE_STRINGBUFFER_CONCATENATION warnings

Replaced string concatenation in loops with StringBuilder in multiple files to improve performance and satisfy SpotBugs checks.
Updated .github/scripts/generate-quality-report.py to fail on this violation.
Fixed compilation errors in ComponentSelector and InnerActive by calling toString() before indexOf/substring on StringBuilder, as CN1's StringBuilder lacks these methods.

Author: google-labs-jules[bot]

CodenameOne/src/com/codename1/ads/InnerActive.java

@@ -148,7 +148,7 @@ public void initService(Ads ads) {
             for (int i = 0; i < klen; i++) {
                 k.append(",").append(keywords[i]);
             }
-            addParam(this, "k", k.substring(1));
+            addParam(this, "k", k.toString().substring(1));
         }
         if (testAds) {
             addParam(this, "test", "1");

CodenameOne/src/com/codename1/ui/ComponentSelector.java

@@ -2231,7 +2231,7 @@ public ComponentSelector addTags(String... tags) {
 
             StringBuilder existingBuilder = new StringBuilder(existing);
             for (String tag : tags) {
-                if (existingBuilder.indexOf(" " + tag + " ") == -1) {
+                if (existingBuilder.toString().indexOf(" " + tag + " ") == -1) {
                     existingBuilder.append(" ").append(tag).append(" ");
                 }
             }