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/Feature/Admin/AdminSettingsTest.php

@@ -33,11 +33,9 @@ test('admin can access settings page', function () {
 test('admin can save settings', function () {
     $admin = User::query()->where('is_admin', true)->first();
 
-    $phpMaxMb = AdminSettings::phpMaxUploadMb();
-
     Livewire::actingAs($admin)
         ->test(AdminSettings::class)
-        ->set('maxFileSize', min(200, $phpMaxMb))
+        ->set('maxFileSize', 200)
         ->set('maxStorageQuota', 50)
         ->set('maxFilesPerShare', 100)
         ->set('maxSizePerShare', 5)
@@ -46,7 +44,7 @@ test('admin can save settings', function () {
         ->assertHasNoErrors()
         ->assertDispatched('toast', type: 'success', title: 'Settings saved successfully.');
 
-    expect(Setting::get('max_file_size'))->toBe((string) (min(200, $phpMaxMb) * 1024 * 1024));
+    expect(Setting::get('max_file_size'))->toBe((string) (200 * 1024 * 1024));
     expect(Setting::get('max_storage_quota'))->toBe((string) (50 * 1024 * 1024 * 1024));
     expect(Setting::get('max_files_per_share'))->toBe('100');
     expect(Setting::get('max_size_per_share'))->toBe((string) (5 * 1024 * 1024 * 1024));
@@ -55,11 +53,9 @@ test('admin can save settings', function () {
 
 test('admin can set system password', function () {
     $admin = User::query()->where('is_admin', true)->first();
-    $phpMaxMb = AdminSettings::phpMaxUploadMb();
-
     Livewire::actingAs($admin)
         ->test(AdminSettings::class)
-        ->set('maxFileSize', $phpMaxMb)
+        ->set('maxFileSize', 100)
         ->set('systemPassword', 'new-system-password')
         ->call('saveSettings')
         ->assertHasNoErrors();
@@ -87,8 +83,7 @@ test('admin can clear system password', function () {
 
 test('settings page loads existing values', function () {
     $admin = User::query()->where('is_admin', true)->first();
-    $phpMaxMb = AdminSettings::phpMaxUploadMb();
-    $testSize = min(40, $phpMaxMb);
+    $testSize = 40;
 
     Setting::set('max_file_size', $testSize * 1024 * 1024);
     Setting::set('max_files_per_share', 75);
@@ -261,3 +256,16 @@ test('switching the password generator off hides its options', function () {
         ->assertDontSeeHtml('wire:model.live="passwordGeneratorType"')
         ->assertDontSeeHtml('data-test="password-example"');
 });
+
+test('a max file size far above PHP\'s upload limit loads and saves unchanged', function () {
+    $admin = User::query()->where('is_admin', true)->first();
+    Setting::set('max_file_size', 15000 * 1024 * 1024);
+
+    Livewire::actingAs($admin)
+        ->test(AdminSettings::class)
+        ->assertSet('maxFileSize', 15000)
+        ->call('saveSettings')
+        ->assertHasNoErrors();
+
+    expect(Setting::get('max_file_size'))->toBe((string) (15000 * 1024 * 1024));
+});