docs: add MIT LICENSE and state the licence in the README (closes #102)

The repository had no licence file at all, which makes publicly readable
code all-rights-reserved by default: nobody may legally use it. That is a
1.0 blocker rather than a nicety, and `LICENSE` was the only file from
`REPO_POLICIES.md`'s required minimum still missing here.

The choice is standing org policy rather than a per-repo call: any public
repo lacking a licence gets MIT, while a private repo with no licence is
already all-rights-reserved and needs nothing. `sneak/dnswatcher` is
public, so MIT.

`LICENSE` carries the canonical MIT text byte-for-byte with only the
copyright line filled in; no clauses added, removed, reworded, or
reflowed. `README.md`'s first line now names the licence, which the
Description requirement in `REPO_POLICIES.md` calls for, and the License
section states MIT and points at the file instead of recording the
decision as pending.

README.md

@@ -1,6 +1,6 @@
 # dnswatcher
 
-dnswatcher is a pre-1.0 Go daemon by [@sneak](https://sneak.berlin) that monitors DNS records, TCP port availability, and TLS certificates, delivering real-time change notifications via Slack, Mattermost, and ntfy webhooks.
+dnswatcher is an MIT-licensed, pre-1.0 Go daemon by [@sneak](https://sneak.berlin) that monitors DNS records, TCP port availability, and TLS certificates, delivering real-time change notifications via Slack, Mattermost, and ntfy webhooks.
 
 > ⚠️ Pre-1.0 software. APIs, configuration, and behavior may change without notice.
 
@@ -486,8 +486,9 @@ Viper for configuration.
 
 ## License
 
-License has not yet been chosen for this project. Pending decision by the
-author (MIT, GPL, or WTFPL).
+dnswatcher is released under the MIT License, Copyright (c) 2026
+[@sneak](https://sneak.berlin). See the [`LICENSE`](./LICENSE) file in the
+repository root for the full text.
 
 ## Author