docs: Update skeleton loader implementation from hyperscript to JavaScript

MIGRATION SUMMARY:
- Moved skeleton loader logic from hyperscript to JavaScript (main.js)
- Changed from htmx:oobAfterSwap to htmx:afterSettle event
- Changed OOB swap from innerHTML to outerHTML for proper element replacement
- Added languageSwitching flag for state tracking
- Added 100ms delay after afterSettle for final render completion

DOCUMENTATION UPDATES:
- 2-MODERN-WEB-TECHNIQUES.md: Updated skeleton loader section with

doc/9-SECURITY.md

@@ -435,7 +435,7 @@ proxy_set_header X-Real-IP $remote_addr;
 **Solution:** This is normal browser behavior. The middleware checks `Referer` header as fallback, which browsers do send for navigation.
 
 For technical API details, see [3-API.md](3-API.md#security-protection).
-
+
 ---
 
 ## Known Security Considerations