Translations: restore key coverage and fix XML validation

Add English fallbacks for 12 missing keys in 41 language files.
Report all missing keys and XML errors before failing validation.

Run four regression tests in CI. All tests and 43 XML files pass.

.github/workflows/xmlvalidate.sh

@@ -116,18 +116,16 @@ for file in "${FILES_TO_PROCESS[@]}"; do
     # 1. Validate XML using fxparser
     log_detail "Validating XML structure..."
     # Capture stdout and stderr, get exit code
-    FXPARSER_OUTPUT=$(fxparser -V "$file" 2>&1)
-    FXPARSER_EXIT_CODE=$?
-
-    if [ "$FXPARSER_EXIT_CODE" -ne 0 ]; then
+    if FXPARSER_OUTPUT=$(fxparser -V "$file" 2>&1); then
+        log_detail_success "XML structure is valid."
+    else
+        FXPARSER_EXIT_CODE=$?
         CURRENT_FILE_PASSES=false
         FAIL_FLAG=true
         log_detail_error "XML Validation Failed for $file (fxparser exit code: $FXPARSER_EXIT_CODE):"
         while IFS= read -r line; do
             log_detail_error "    $line"
         done <<< "$FXPARSER_OUTPUT"
-    else
-        log_detail_success "XML structure is valid."
     fi
 
     # 2. Check for invalid backslash escape sequences
@@ -165,7 +163,7 @@ for file in "${FILES_TO_PROCESS[@]}"; do
                 log_detail_error "Key '$key_entry' (from $COMMON_FILE) not found in $file"
                 CURRENT_FILE_PASSES=false
                 FAIL_FLAG=true
-                ((KEYS_MISSING_IN_CURRENT_FILE++))
+                KEYS_MISSING_IN_CURRENT_FILE=$((KEYS_MISSING_IN_CURRENT_FILE + 1))
             fi
         done
         if [ "$KEYS_MISSING_IN_CURRENT_FILE" -eq 0 ]; then