Bump OpenProject version

Editing docker-compose.yml directly is overwritten on every pull.
The correct approach is a separate Dockerfile.gitea (owned by the
operator) referenced from docker-compose.override.yml, which is
never touched by upstream updates.

README.md

@@ -26,8 +26,9 @@ When a pull request in Gitea references an OpenProject work package (via a URL o
 
 In a pull request title, description, or comment, reference a work package using:
 
-- A full URL: `https://openproject.example.com/work_packages/42`
-- A short reference: `OP#42` or `OP#PROJ-42`
+- Its semantic ID: `KS-10`, `PROJ-42` — matched automatically, no prefix needed
+- A prefixed numeric ID: `OP#42` — prefix required to avoid collision with Gitea issue numbers
+- A full OpenProject URL: `https://openproject.example.com/work_packages/42`
 
 Multiple references in the same text are all picked up.
 
@@ -57,9 +58,84 @@ openproject config:set RECOMPILE_ANGULAR_ASSETS=true
 sudo openproject configure
 ```
 
-### Docker installation
+### Docker / docker-compose installation
 
-Follow the [OpenProject Docker plugin guide](https://www.openproject.org/docs/installation-and-operations/installation/docker/#openproject-plugins). Add the gem to your custom Gemfile and rebuild the image.
+The official OpenProject Docker image bakes all gems and frontend assets in at
+build time, so installing a third-party plugin requires building a custom image.
+The `docker-compose.yml` provided by OpenProject is overwritten on every update,
+so all local changes go into `docker-compose.override.yml` and a separate
+`Dockerfile` that you own.
+
+#### 1. Clone the plugin
+
+```shell
+git clone https://github.com/quafzi/openproject-gitea-plugin.git \
+  openproject-gitea-plugin
+```
+
+Place it anywhere convenient — this guide assumes it sits next to your
+`docker-compose.yml`.
+
+#### 2. Create `Dockerfile.gitea`
+
+```dockerfile
+FROM openproject/openproject:17
+
+USER root
+
+# Copy the plugin source into the image
+COPY --chown=app:app openproject-gitea-plugin \
+     /app/modules/gitea_integration
+
+# Register the gem and recompile assets
+RUN echo 'group :opf_plugins do\n  gem "openproject-gitea_integration", path: "modules/gitea_integration"\nend' \
+    > /app/Gemfile.plugins && \
+    cd /app && \
+    bundle install --without development test && \
+    RAILS_ENV=production bundle exec rake \
+      openproject:plugins:register_frontend \
+      assets:precompile
+
+USER app
+```
+
+#### 3. Create `docker-compose.override.yml`
+
+This file is never touched by OpenProject updates. Point both `web` and
+`worker` at your custom image — they must use the same image so the plugin is
+loaded in both processes.
+
+```yaml
+services:
+  web:
+    build:
+      context: .
+      dockerfile: Dockerfile.gitea
+    image: openproject-with-gitea:latest
+
+  worker:
+    build:
+      context: .
+      dockerfile: Dockerfile.gitea
+    image: openproject-with-gitea:latest
+```
+
+#### 4. Build and start
+
+```shell
+docker compose build
+docker compose up -d
+docker compose exec web bundle exec rails db:migrate
+```
+
+#### Updating the plugin
+
+```shell
+cd openproject-gitea_integration && git pull && cd ..
+docker compose build --no-cache
+docker compose up -d
+docker compose exec web bundle exec rails db:migrate
+```
 
 ### Manual / monorepo installation