Server: faster releases (cache hashes), per-version skip, longer signed-URL TTL

- gate.php : ETag now derived from size+mtime instead of md5_file($zip).
  Previously the gate hashed the entire 14 GB ZIP on every HEAD/GET call
  (including each of 8 parallel segments) → 30s-5min preparation lag for
  clients before the first byte. Now <1ms per request.
- SignManifest : disk-backed cache for SHA-256 keyed by (path,size,mtime).
  Re-signing 5×14 GB versions used to take ~25 min, now ~1s when nothing
  changed. New "Force re-hash" toggle in admin to ignore the cache.
- versions.php : per-row "🔁 Hash" button to sign a single version, plus
  a "⚙ Hash" dropdown to toggle hashAlgorithm:none for builds where the
  user accepts skipping client-side verification (manifest stays signed
  Ed25519, only the per-ZIP SHA-256 verification is bypassed).
- DownloadUrl.php : signed-URL TTL bumped 1h → 6h to cover slow ADSL users
  who need >1h to finish a 14 GB download.
- .gitignore : track server/builds/.htaccess + gate.php (still ignore the
  actual ZIP/exe binaries).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/tools/sign-manifest.php

@@ -2,7 +2,11 @@
 /**
  * Wrapper CLI pour PSLauncher\Tools\SignManifest.
  *
- * Usage : cd ~/www/PS_Launcher && php tools/sign-manifest.php
+ * Usage :
+ *   cd ~/www/PS_Launcher && php tools/sign-manifest.php
+ *   php tools/sign-manifest.php --scope=launcher       # ne re-signe que la section launcher
+ *   php tools/sign-manifest.php --scope=versions       # ne re-signe que les builds Proserve
+ *   php tools/sign-manifest.php --force                # ignore le cache, recalcule tous les SHA-256
  *
  * Le backoffice admin appelle directement la classe (pas d'exec).
  */
@@ -10,7 +14,15 @@ declare(strict_types=1);
 
 require __DIR__ . '/SignManifest.php';
 
+$scope = 'all';
+$force = false;
+foreach (array_slice($argv, 1) as $arg) {
+    if ($arg === '--force' || $arg === '-f') $force = true;
+    elseif (str_starts_with($arg, '--scope=')) $scope = substr($arg, 8);
+    elseif (in_array($arg, ['versions', 'launcher', 'all'], true)) $scope = $arg;
+}
+
 $signer = new \PSLauncher\Tools\SignManifest(dirname(__DIR__));
-$result = $signer->run();
+$result = $signer->run($scope, $force);
 foreach ($result['log'] as $line) echo $line . "\n";
 exit($result['ok'] ? 0 : 1);