refactor: replace numeric translation keys with named keys

- Extract shared i18n.sh library with tr() function (replaces 5 duplicated text_lang functions)
- Replace numeric IDs (001, 002, ...) with human-readable keys (already_started, delete, etc.)
- Update all language files (en_US, en_GB, de_DE) to use named key format
- Update all scripts (jdautoenc, rename, addrename, removerename, config) to use tr() from i18n.sh

i18n.sh

@@ -0,0 +1,68 @@
+# Shared i18n library for JDownloader-Autoenc-rename
+# Source this file from your scripts, then use tr("key") to get translations.
+
+# Determine script name (jdautoenc, rename, addrename, removerename, config)
+SCRIPT_NAME=$(basename "${BASH_SOURCE[1]}" .sh 2>/dev/null)
+if [[ -z "$SCRIPT_NAME" ]]; then
+  SCRIPT_NAME=$(basename "$0" .sh 2>/dev/null)
+fi
+
+# Find language folder
+if [[ -n "$language_folder" ]]; then
+  : # already set
+elif [[ -n "$JDAutoConfig" && -f "$JDAutoConfig" ]]; then
+  language_folder=$(grep "language_folder=" "$JDAutoConfig" 2>/dev/null | sed 's/.*=//g')
+fi
+
+# Determine language
+if [[ -z "$language" ]]; then
+  if [[ -n "$JDAutoConfig" && -f "$JDAutoConfig" && -n "$(grep "language=" "$JDAutoConfig" 2>/dev/null | sed 's/.*=//g')" ]]; then
+    language=$(grep "language=" "$JDAutoConfig" | sed 's/.*=//g')
+  else
+    language=$(locale 2>/dev/null | head -n 1 | sed 's/.*=\|\..*//g')
+  fi
+fi
+
+if [[ "$language" == "C" ]] || [[ ! -d "$language_folder/$language" ]]; then
+  language=en_US
+fi
+
+# The lang file for the current script
+LANG_FILE="$language_folder/$language/${SCRIPT_NAME}.lang"
+FALLBACK_LANG_FILE="$language_folder/en_US/${SCRIPT_NAME}.lang"
+
+tr() {
+  local key="$1"
+
+  # Try local lang file
+  if [[ -f "$LANG_FILE" ]]; then
+    local result
+    result=$(grep "^${key} " "$LANG_FILE" 2>/dev/null | head -n 1 | sed "s/^${key} //")
+    if [[ -n "$result" ]]; then
+      echo "$result"
+      return
+    fi
+  fi
+
+  # Try fallback (en_US)
+  if [[ -f "$FALLBACK_LANG_FILE" ]]; then
+    local result
+    result=$(grep "^${key} " "$FALLBACK_LANG_FILE" 2>/dev/null | head -n 1 | sed "s/^${key} //")
+    if [[ -n "$result" ]]; then
+      echo "$result"
+      return
+    fi
+  fi
+
+  # Try remote fallback
+  local remote_url="https://raw.githubusercontent.com/Pakobbix/JDownloader-Autoenc-rename/main/lang/en_US/${SCRIPT_NAME}.lang"
+  local result
+  result=$(curl -s "$remote_url" 2>/dev/null | grep "^${key} " | head -n 1 | sed "s/^${key} //")
+  if [[ -n "$result" ]]; then
+    echo "$result"
+    return
+  fi
+
+  # Return the key itself as last resort
+  echo "$key"
+}