Fix installation directory handling and clarify defaults

- Fixed bootstrap-installer to prompt for installation directory with /opt/trans-install as default
- Updated main-installer to detect and use existing installation path from service file
- Modified config-module to use installation directory from environment or default to /opt/trans-install
- Updated README with clear information about the default installation path
- Bumped version to 2.0.7

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

main-installer.sh

@@ -47,6 +47,14 @@ fi
 # Check for service file (secondary indicator)
 if [ -f "/etc/systemd/system/transmission-rss-manager.service" ]; then
   INSTALLATION_DETECTED=true
+  
+  # Check if the service points to /opt/trans-install
+  if grep -q "/opt/trans-install" "/etc/systemd/system/transmission-rss-manager.service"; then
+    # Set INSTALL_DIR to match existing service file
+    INSTALL_DIR="/opt/trans-install"
+    log "INFO" "Found existing installation at /opt/trans-install - using this as installation directory"
+    export INSTALL_DIR
+  fi
 fi
 
 # Check for data directory (tertiary indicator)