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/config.md

@@ -35,9 +35,12 @@ providers:
     paths: [~/work/infra]
     include: ["secrets/**"]
     exclude: ["**/testdata/**"]
+share:                 # sharing env files as encrypted links
+  key: lazysecrets://azure/kv-team.vault.azure.net/secrets/env-share  # for repos naming none
 ```
 
-More, each on its own page: [repos](repos.md) (`providers.repos`), the
+More, each on its own page: [repos](repos.md) (`providers.repos`),
+[sharing env files](links.md#sharing-env-files) (`share`), the
 [link handler](links.md#from-the-browser-and-chat) (`linkHandler`),
 [keybindings](keys.md#rebinding-keys) (`keybinding`) and
 [custom commands](custom-commands.md) (`customCommands`).