Document installing cv4pve-tui as a uv tool

The README gets an "Install" section: install with uv tool from the
Gitea repo or from a local checkout, then upgrade and uninstall. The
"Run" section says to use `cv4pve-tui` when installed and
`uv run cv4pve-tui` from a checkout.

Verified by installing into throwaway tool dirs (UV_TOOL_DIR and
UV_TOOL_BIN_DIR under /tmp): `uv tool install .` gave a cv4pve-tui
binary. Started from /tmp in a pseudo-terminal, it drew the guest
frame and ran until it was stopped. The pyproject metadata (entry
point, readme, requires-python) was already enough.

Closes #17

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -11,8 +11,25 @@ It shells out to `cv4pve-cli` and uses its current context (`cv4pve-cli config u
 it stores no credentials itself. Tested with cv4pve-cli 2.4.0; with another version the app
 warns at startup, because it parses output formats that are not a stable API.
 
+## Install
+
+Needs [uv](https://docs.astral.sh/uv/) and a working `cv4pve-cli` on `PATH`.
+
+```sh
+uv tool install git+https://git.duckboot.net/Duckboot/cv4pve-cli-tui
+cv4pve-tui                      # from any directory
+uv tool upgrade cv4pve-tui      # later: get the newest main
+uv tool uninstall cv4pve-tui
+```
+
+From a local checkout instead: `uv tool install .` (add `--force` to reinstall after
+changes).
+
 ## Run
 
+
+Installed: `cv4pve-tui`. From a checkout without installing:
+
 ```sh
 uv run cv4pve-tui
 ```