feat: link each changelog entry to its PR and commit (#11)

Like Immich's and RomM's release notes: every changelog entry now links to its pull request and its commit, in `CHANGELOG.md` and in the release notes on Gitea:

```
- Search with fzf's scoring and query syntax ([#11](…/pulls/11)) ([65dc2d7](…/commit/65dc2d7…))
```

- `cliff.toml`: the entry template adds the short commit hash as a link; a postprocessor turns the squash commit's `(#N)` into a link to the PR.
- The app shows release notes as text (`U`, and the status pane's changelog to come), so `Release.Notes()` turns Markdown links back into their text: `Search (#11) (65dc2d7)`.

Checked with `git cliff --unreleased` on main: every entry since v0.1.0 gets both links. Test for the link stripping.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>
Reviewed-on: #11

docs/keys.md

@@ -112,6 +112,12 @@ that; there `j`/`k`, `/` and `y` work on its rows, and `shift+tab` goes
 back. A value you reveal stays in view whichever pane you're in, until
 it's hidden.
 
+On top, the status pane (`0`) shows the version, a newer release and how
+your accounts are doing. Focused, the right pane lists more: the version
+and updates (`U`), each account (`L` on one that needs it signs in), the
+config, state and cache files (`e` opens one in your editor), and links
+to the docs, source and issues (`o` opens one). `y` copies any of them.
+
 | Key | Action |
 |---|---|
 | `ctrl+←`/`ctrl+→` or `<`/`>` | move the divider between the left panes and the detail pane |