feat: share env files as encrypted links

S → f on a repo, an env file or a key in one copies a
lazysecrets://share link holding the env files, encrypted (age) with
a secret's value: whoever can read that secret can open it. The key is
share.key in the repo's .lazysecrets.yaml, else in the config, else
picked when sharing; on Azure the link pins its version. Opening one
says what it holds, decrypts when asked, and saves the files in the
clone of the repo (or a folder chosen), replacing existing ones only
when asked. lazysecrets share prints a link from the command line.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/keys.md

@@ -54,7 +54,7 @@ match case exactly.
 | `v` | versions of the selected item (Azure); `space`/`y`/`Y` then act on that version; `esc`, `⌫` or `v` to go back |
 | `o` | open the selected item in the browser (over SSH: copy the link) |
 | `e` | open the selected SOPS or `.env` file, or a secret's file at its line ([how](repos.md#opening-files)) |
-| `s` / `S` | copy a [link](links.md) to the selected item / share menu |
+| `s` / `S` | copy a [link](links.md) to the selected item / share menu (also env files, [encrypted](links.md#sharing-env-files)) |
 | `ctrl+o` | open a link or reference (or just paste one) |
 | `x` | [custom commands](custom-commands.md) |
 | `L` | sign in again (shown when a login has expired) |