ci: update runner-image + repo path to public/ namespace

Repos moved to public/ on Gitea: public/runner-image (CI image)
and public/code-crispies (this repo). Updates workflow image refs,
spec hyperlinks, README, and compose tags.

README.md

@@ -44,7 +44,7 @@ Code Crispies is a web-based learning platform designed to help users master HTM
 
 1. Clone the repository:
    ```bash
-   git clone https://git.librete.ch/libretech/code-crispies.git
+   git clone https://git.librete.ch/public/code-crispies.git
    cd code-crispies
    ```
 
@@ -236,7 +236,7 @@ docker compose up -d
 
 ```sh
 ssh netcup
-git clone ssh://tengo@git.librete.ch:41240/libretech/code-crispies.git /srv/cc
+git clone ssh://tengo@git.librete.ch:41240/public/code-crispies.git /srv/cc
 cd /srv/cc
 cp .env.example .env
 $EDITOR .env   # fill VITE_SUPABASE_URL + VITE_SUPABASE_ANON_KEY