Encrypt uploads in the browser and send them in chunks

A 6 GB upload kept a customer waiting long after its progress bar
reached 100%. The server wrote every upload three times: PHP's
temporary file, Livewire's copy of it ("Processing files...") and the
encrypted file ("Create Share Link"), each a full rewrite of a slow
disk. The unencrypted copy also stayed behind in livewire-tmp.

Now the uploader's browser encrypts each file in 16 MB chunks with
WebCrypto and PUTs them one at a time; the server checks each chunk in
memory and writes it once, already encrypted. Creating the share only
wraps its key and saves the options. A 200 MB upload through the
Docker image took 2.8 s, and its download matched byte for byte.

- SEALCHK2: a 19-byte header (chunk size, 7-byte nonce prefix), then
  ciphertext and tag per chunk. Each nonce holds the chunk index and a
  last-chunk flag (the STREAM construction), so cut or reordered files
  fail to decrypt. SEALCHK1 and the single-block format still read.
- Envelope encryption: one random key per share. With a password it is
  wrapped with Argon2id (sodium, libsodium's interactive limits) in
  shares.wrapped_key, which names its parameters. Password shares from
  before keep their PBKDF2-derived key.
- The upload page registers each selection with FileUploader into a
  pending share of its own, lists the files with their progress, retries
  a failed chunk after 1-16 s, then offers Retry; Remove and Cancel
  abort. UploadChunkController only accepts chunks from the session that
  started the share: a repeat is acknowledged, a skip gets 409 with the
  count stored. Chunks go out as Blobs, which Chromium sends about eight
  times faster than ArrayBuffers.
- Uploads need a secure context: over plain HTTP the page says HTTPS is
  needed and takes no files. The Docker image gains AUTO_HTTPS, which
  serves Let's Encrypt on 443 for SERVER_NAME and redirects 80; without
  it the container stays on HTTP 80 behind a proxy. docker/Caddyfile was
  never loaded and is gone; docker/healthcheck.sh covers both modes.
- "Download all" streams the ZIP with maennchen/zipstream-php (STORE,
  ZIP64) instead of decrypting whole files into memory and writing the
  archive unencrypted to /tmp.
- Pending shares count towards the quota, stay out of the admin
  dashboard and 404 everywhere else. shares:cleanup deletes uploads idle
  for 4 hours and Livewire temporary files older than that.
- PHP's upload limits no longer cap the admin's max file size and
  default to 64M; LIVEWIRE_MAX_UPLOAD_TIME is gone and
  UPLOAD_CHUNK_SIZE_MB is new.
- Tests cover the format, key wrapping, registration limits, the chunk
  endpoint's answers, completing a share, the streamed ZIP, cleanup,
  and in Chromium a real chunked upload and the HTTPS warning; the
  selected-files overflow test runs again. README, website, CHANGELOG
  and .ai/rules follow.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/Livewire/Admin/AdminSettings.php

@@ -70,10 +70,7 @@ class AdminSettings extends Component
     {
         $this->colorProfile = Scheme::profile() ?? '';
         $this->defaultExpiration = Setting::get('default_expiration', '') ?? '';
-        $this->maxFileSize = min(
-            (int) Setting::get('max_file_size', 100 * 1024 * 1024) / (1024 * 1024),
-            self::phpMaxUploadMb(),
-        );
+        $this->maxFileSize = (int) Setting::get('max_file_size', 100 * 1024 * 1024) / (1024 * 1024);
         $this->maxStorageQuota = (int) Setting::get('max_storage_quota', 20 * 1024 * 1024 * 1024) / (1024 * 1024 * 1024);
         $this->maxFilesPerShare = (int) Setting::get('max_files_per_share', 50);
         $this->maxSizePerShare = (int) Setting::get('max_size_per_share', 2 * 1024 * 1024 * 1024) / (1024 * 1024 * 1024);
@@ -91,34 +88,11 @@ class AdminSettings extends Component
         $this->passphraseSeparator = $passwordOptions['separator'];
     }
 
-    public static function phpMaxUploadMb(): int
-    {
-        $parse = function (string $value): int {
-            $value = trim($value);
-            $last = strtolower($value[strlen($value) - 1]);
-            $num = (int) $value;
-
-            return match ($last) {
-                'g' => $num * 1024,
-                'm' => $num,
-                'k' => max(1, (int) ($num / 1024)),
-                default => max(1, (int) ($num / (1024 * 1024))),
-            };
-        };
-
-        $upload = $parse(ini_get('upload_max_filesize') ?: '2M');
-        $post = $parse(ini_get('post_max_size') ?: '8M');
-
-        return min($upload, $post);
-    }
-
     public function saveSettings(): void
     {
-        $phpMaxMb = self::phpMaxUploadMb();
-
         $validated = $this->validate([
             'colorProfile' => ['required', 'string', Rule::in(array_keys(Scheme::profiles()))],
-            'maxFileSize' => ['required', 'integer', 'min:1', 'max:'.$phpMaxMb],
+            'maxFileSize' => ['required', 'integer', 'min:1'],
             'maxStorageQuota' => ['required', 'integer', 'min:1'],
             'maxFilesPerShare' => ['required', 'integer', 'min:1'],
             'maxSizePerShare' => ['required', 'integer', 'min:1'],
@@ -127,7 +101,6 @@ class AdminSettings extends Component
             'siteLogo' => ['nullable', 'file', 'mimes:png,jpg,jpeg,gif,webp', 'max:2048'],
             ...$this->passwordGeneratorRules(),
         ], [
-            'maxFileSize.max' => __('Cannot exceed the PHP limit of :max MB. Increase upload_max_filesize and post_max_size in your PHP configuration.', ['max' => $phpMaxMb]),
             ...$this->passwordGeneratorMessages(),
         ]);
 
@@ -276,7 +249,6 @@ class AdminSettings extends Component
         return view('livewire.admin.admin-settings', [
             'hasSystemPassword' => (bool) Setting::get('system_password'),
             'currentLogo' => Setting::get('site_logo'),
-            'phpMaxUploadMb' => self::phpMaxUploadMb(),
             'passwordExample' => $passwordPreviewOptions ? $passwordGenerator->generate($passwordPreviewOptions) : null,
             'passwordEntropy' => $passwordPreviewOptions ? $passwordGenerator->entropyBits($passwordPreviewOptions) : null,
         ]);