feat: one-command installers for macOS, Linux and Windows

deployment/install.sh (curl | bash) and install.ps1 (irm | iex) check for
Docker, install uv when it is missing or older than 0.8 (pinned 0.12.15 via
Astral's installer), install or upgrade the docsgpt package with
`uv tool install`, and hand the terminal to `docsgpt up` with any arguments.
On Linux without Docker the shell installer offers get.docker.com. Both run
entirely inside a function, so a download cut short runs nothing.

Releases attach both scripts next to the Compose file, which is where
docs.ac/install and docs.ac/install.ps1 will point. installer-lint.yml runs
shellcheck and the PowerShell parser; docker-image-verify.yml now installs
through install.sh. README, Quickstart, Docker-Deploying and the changelog
lead with the one-liner.

README.md

@@ -80,9 +80,33 @@ Calling all developers and GenAI innovators! The **DocsGPT Lighthouse Program**
 ## QuickStart
 
 > [!Note]
-> Make sure you have [Docker](https://docs.docker.com/engine/install/) installed
+> DocsGPT runs on [Docker](https://docs.docker.com/engine/install/). The installer checks for it first.
 
-A more detailed [Quickstart](https://docs.docsgpt.cloud/quickstart) is available in our documentation
+**macOS and Linux:**
+
+```bash
+curl -fsSL https://docs.ac/install | bash
+```
+
+**Windows (PowerShell):**
+
+```powershell
+irm https://docs.ac/install.ps1 | iex
+```
+
+The installer gets [uv](https://docs.astral.sh/uv/), installs the `docsgpt` Python package with it, and runs `docsgpt up`. That asks who should reach DocsGPT (only this computer, your network, or a domain with HTTPS) and which model provider to use, then starts it, at http://localhost:7091 for a local install. Afterwards, `docsgpt status`, `docsgpt logs`, `docsgpt upgrade`, `docsgpt down` and `docsgpt uninstall` manage it.
+
+To read the script before running it:
+
+```bash
+curl -fsSL https://docs.ac/install -o install.sh
+less install.sh
+bash install.sh
+```
+
+A more detailed [Quickstart](https://docs.docsgpt.cloud/quickstart) is available in our documentation.
+
+### From a clone, with the setup script
 
 1. **Clone the repository:**