fix: changelog encoding (mojibake) + limit display to 5 versions back

Rebuilt changelog data from manifest JSON files to fix garbled Polish
characters. Converted changelog.php from static HTML to PHP script that
filters entries by instance version (?ver= parameter).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

build-update.ps1

@@ -368,9 +368,9 @@ if (Test-Path $versionsFile) {
     Write-Ok "Zaktualizowano versions.php: `$current_ver = $versionInt"
 }
 
-# --- 14. Aktualizacja changelog.php ---
+# --- 14. Aktualizacja changelog-data.html ---
 
-$changelogFile = "updates/changelog.php"
+$changelogFile = "updates/changelog-data.html"
 if (Test-Path $changelogFile) {
     $dateStr = Get-Date -Format "dd.MM.yyyy"
     $newEntry = "<b>ver. $versionNumber - $dateStr</b><br />`n$ChangelogEntry`n<hr>`n"
@@ -378,7 +378,7 @@ if (Test-Path $changelogFile) {
     $changelogContent = Get-Content $changelogFile -Raw
     $changelogContent = $newEntry + $changelogContent
     [System.IO.File]::WriteAllText($changelogFile, $changelogContent, $Utf8NoBom)
-    Write-Ok "Zaktualizowano changelog.php"
+    Write-Ok "Zaktualizowano changelog-data.html"
 }
 
 # --- 15. Cleanup ---