feat: Stage 1 scaffold — config, API client, placeholder TUI

Sets up the full project structure following the hactl/gokapi-tui
architecture: strict Elm-pattern Bubbletea TUI, YAML config at
~/.config/terdut-tui/config.yaml, REST API client with Bearer auth,
self-update via GitHub Releases, and a three-section tab placeholder
(Alerts / Schedule / Users) that verifies server connectivity on startup.

README.md

@@ -0,0 +1,53 @@
+# terdut-tui
+
+A terminal user interface for [terdut-server](https://github.com/terdut-server). Communicates with the server over its REST API.
+
+Written in Go using [Bubbletea](https://github.com/charmbracelet/bubbletea).
+
+## Features
+
+- **Alert dashboard** — live view of firing and resolved alerts with auto-refresh
+- **Alert actions** — acknowledge, comment, and view per-alert statistics
+- **On-call schedule** — visual calendar of who is on duty, assign and remove entries
+- **User management** — add and remove users, manage API keys
+
+## Installation
+
+Download the latest release binary for your platform from the [releases page](https://github.com/yeniklas/terdut-tui/releases), or build from source:
+
+```bash
+go install github.com/yeniklas/terdut-tui@latest
+```
+
+## Configuration
+
+Create `~/.config/terdut-tui/config.yaml`:
+
+```yaml
+server_url: https://terdut.example.com
+api_key: <your-api-key>
+refresh_interval: 30  # seconds, optional
+```
+
+The API key is generated in terdut-server. See the server documentation for how to bootstrap a user and issue an API key.
+
+## Usage
+
+```
+terdut-tui                 start the TUI
+terdut-tui --version       print version
+terdut-tui --self-update   update to the latest release
+```
+
+### Keybindings
+
+| Key | Action |
+|-----|--------|
+| `j` / `↓` | Move down |
+| `k` / `↑` | Move up |
+| `tab` | Switch section (Alerts / Schedule / Users) |
+| `enter` | Select / open detail |
+| `esc` | Go back |
+| `r` | Refresh |
+| `f` | Filter / cycle filter |
+| `q` | Quit |