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>

internal/ui/keys/keys.go

@@ -117,7 +117,7 @@ func (m *Map) Actions() []Action {
 		a(Lists, "edit", &m.Edit, "open file", "secrets", "Open the selected SOPS or .env file, or the file of the selected secret at its line. SOPS files open with sops edit. Others open in the nvim lazysecrets runs in (quitting lazysecrets), else in $VISUAL or $EDITOR, else in the system's default app."),
 
 		a(Lists, "share", &m.Share, "copy link", "share", "Copy a lazysecrets:// link to the selected subscription, workspace, vault, scope or secret, for sharing. From the versions view the link is pinned to that version."),
-		a(Lists, "shareMenu", &m.ShareMenu, "share", "share", "Choose what to share: the lazysecrets link, the plain Key Vault URL, the config reference, or the web page."),
+		a(Lists, "shareMenu", &m.ShareMenu, "share", "share", "Choose what to share: the lazysecrets link, the plain Key Vault URL, the config reference, the web page, or env files as an encrypted link."),
 		a(Lists, "openLink", &m.OpenRef, "open link", "share", "Open a lazysecrets:// link, Key Vault URL or reference. Pasting one into lazysecrets does the same."),
 
 		a(Lists, "dividerLeft", &m.SplitLeft, "divider left", "layout", "Move the divider between the left panes and the detail pane to the left."),