Generate share passwords and offer them again beside the new link

Uploaders no longer have to make up a share password. With "Password
protect" on, the upload page has Generate and Copy under the field, and
the page the upload leads to offers the password once more beside the
link: masked, with the same copy button at the end of the field as the
link's. The password also derives the share's encryption key and only
its hash is stored, so a lost one means files nobody can open.

- PasswordGeneratorService draws from Random\Randomizer's secure engine.
  Characters are drawn uniformly and redrawn until every chosen set
  appears; passphrases come from EFF's large word list (CC BY 3.0 US,
  credited in the README), without its four hyphenated words.
- Admin settings gain a "Share Passwords" card: mode (off, on request,
  prefilled as protection is switched on), kind (characters: length
  12–64, the sets, look-alikes left out; passphrase: 4–10 words and a
  separator), and an example with its estimated entropy that follows the
  form before saving. Fields the chosen mode or kind hides are excluded
  from validation and keep their saved value. The default is on
  request, 20 letters and numbers without look-alikes.
- FileUploader flashes the password encrypted with the share's token;
  ShareCreated shows it only when the token matches, so a reload or any
  other visitor sees nothing. Crypt covers installs without
  SESSION_ENCRYPT, which the Docker setup does not set.
- The symbol set leaves out what chat apps turn into formatting and
  what breaks inside quotes, so a pasted password arrives unchanged.
- app.css imports group.css for <x-group>; .ai/rules/views.md records
  that <x-group> drops data-test and other attributes.
- Tests cover the generator, the admin card's saving, validation and
  example, prefill and generate on the upload page, the flash, and in
  Chromium Generate and Copy on the upload page and the masked copy on
  the share page. The admin settings page now has six headed sections.

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

README.md

@@ -19,7 +19,7 @@ A simple, self-hosted file sharing solution built with Laravel. Upload files, ge
 - **File Uploading** — Drag & drop or browse to upload single/multiple files and folders with real-time progress
 - **Shareable Links** — Each upload generates a unique link for recipients, also as a QR code (saved as a PNG) or through the device's share sheet
 - **Encryption at Rest** — Files are encrypted on the server as they arrive, with AES-256-GCM (chunked, streaming); with a share password the key is derived from it and never stored. It is not end-to-end encryption: the server handles the files unencrypted while they are uploaded and downloaded
-- **Password Protection** — Optionally protect shares with a password
+- **Password Protection** — Optionally protect shares with a password, typed or generated (random characters or a passphrase, as the admin configures) and copied on the upload page or next to the new link
 - **Expiration** — Shares auto-expire after a configurable duration (1 hour to 30 days)
 - **Download Limits** — Set a maximum number of downloads per share
 - **ZIP Downloads** — Download all files in a share as a single ZIP archive
@@ -152,3 +152,5 @@ Add the scheduler to your crontab:
 ## License
 
 This project is open-source software licensed under the [MIT License](LICENSE).
+
+Generated passphrases draw from the [EFF Large Wordlist](https://www.eff.org/deeplinks/2016/07/new-wordlists-random-passphrases) by the Electronic Frontier Foundation, licensed under [CC BY 3.0 US](https://creativecommons.org/licenses/by/3.0/us/) (`resources/wordlists/eff-large-wordlist.txt`, without its four hyphenated words).