feat(send): add role for self-hosted Send file-share service

Deploys timvisee/send with a Redis backend behind Traefik. Supports
local-disk or S3 storage (e.g. via the garage role). Uses the shared
`*_domains` list convention so the router can accept internal *.int.*
names alongside the canonical BASE_URL host.

roles/send/README.md

@@ -0,0 +1,60 @@
+Send
+====
+
+Deploys a self-hosted [Send](https://github.com/timvisee/send) instance
+(timvisee fork of the discontinued Mozilla Send) with a Redis backend
+behind Traefik, using Docker Compose.
+
+Requirements
+------------
+
+- Docker + `docker compose` plugin on the target host
+- Traefik (role `digitalboard.core.traefik`) reachable via an external
+  Docker network named `proxy` (default)
+- DNS for each entry in `send_domains` pointing at the reverse proxy
+- Optional: a Garage S3 bucket if `send_storage_backend: s3`
+
+Role Variables
+--------------
+
+Important defaults (see `defaults/main.yml` for the full list):
+
+| Variable | Default | Description |
+|---|---|---|
+| `send_domains` | `["send.local.test"]` | FQDNs the router accepts; first entry is the canonical BASE_URL |
+| `send_image` | `registry.gitlab.com/timvisee/send:latest` | Send container image |
+| `send_max_file_size` | `1073741824` | Max upload size in bytes (1 GiB) |
+| `send_max_expire_seconds` | `604800` | Max share lifetime (7 d) |
+| `send_storage_backend` | `local` | `local` (volume) or `s3` |
+| `send_s3_*` | `""` | S3 endpoint/bucket/key/secret (when backend is `s3`) |
+| `send_use_ssl` | `true` | Issue Traefik labels for the `websecure` entrypoint |
+
+Dependencies
+------------
+
+None.
+
+Example Playbook
+----------------
+
+```yaml
+- hosts: send_servers
+  become: true
+  roles:
+    - digitalboard.core.send
+```
+
+With S3 (Garage) backend:
+
+```yaml
+send_storage_backend: s3
+send_s3_endpoint: "http://{{ hostvars['backend']['garage_s3_domain'] }}"
+send_s3_bucket: "send"
+send_s3_access_key: "{{ lookup('digitalboard.core.garage_credentials', 'send', host='backend')['key_id'] }}"
+send_s3_secret_key: "{{ lookup('digitalboard.core.garage_credentials', 'send', host='backend')['secret_key'] }}"
+```
+
+License
+-------
+
+MIT