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>

tests/Browser/SealShareTest.php

@@ -3,6 +3,7 @@
 use App\Models\Setting;
 use App\Models\Share;
 use App\Models\User;
+use App\Services\FileEncryptionService;
 use App\Services\ShareService;
 use Illuminate\Http\UploadedFile;
 use Illuminate\Support\Facades\Crypt;
@@ -28,8 +29,28 @@ test('files dragged over the drop zone turn its shape into a burst', function ()
         ->assertNoJavaScriptErrors();
 });
 
-// Pest's in-process server does not store a multipart upload, so the upload itself is covered by
-// FileUploadTest; this picks up where it ends, on the page the upload leads to.
+test('a chosen file is encrypted in the browser, sent in chunks and shared with its exact content', function () {
+    // Pest's in-process server takes request bodies up to 128 KB: 64 KB chunks send this file in three.
+    config(['uploads.chunk_size' => 64 * 1024]);
+    $content = random_bytes(150 * 1024);
+    $path = sys_get_temp_dir().'/sealshare-browser-upload-'.uniqid().'.bin';
+    file_put_contents($path, $content);
+
+    $page = ready(visit('/upload'));
+    $page->attach('[data-test="file-input"]', $path)
+        ->waitForText('Uploaded')
+        ->click('[data-test="create-share"]')
+        ->waitForText('Share Created!')
+        ->assertNoJavaScriptErrors();
+
+    $file = Share::query()->sole()->files->sole();
+    expect($file->uploaded_chunks)->toBe(3);
+    $stored = app(FileEncryptionService::class)->decryptedChunks(app(ShareService::class)->storedFilePath($file), $file->share->encryption_key);
+    expect(implode('', iterator_to_array($stored, false)))->toBe($content);
+
+    unlink($path);
+});
+
 test('a new share\'s link can be copied from the page the upload leads to', function () {
     $share = app(ShareService::class)->createShare(
         [['file' => UploadedFile::fake()->create('contract.pdf', 80), 'relativePath' => null]],