docs: use local Debian packages for bare-metal deployment

The Debian packages benefit from security support and should be much easier to install for most users.

Currently all requirements of Aura Engine are packaged in Debian. Thus the virtualenv-related documentation snippets can be removed.

docs/bare-metal-installation.md

@@ -24,9 +24,7 @@ Aura Engine runs on any modern Debian-based OS. It requires at least
 - [Python 3.8+](https://www.python.org/downloads/release/python-380/)
 - [`pip`](https://pip.pypa.io/en/stable/)
 - [`git`](https://git-scm.com/)
-- 'python3.8-venv' or [`virtualenv`](https://pypi.org/project/virtualenv/)
-- `python3-wheel`
-- [PostgreSQL 12+](https://www.postgresql.org/)
+- [PostgreSQL 13+](https://www.postgresql.org/)
 
 
 **Setting up the project structure**
@@ -46,24 +44,16 @@ If you are developing engine you also might want the projects `steering`, `dashb
 
 ## Preparation
 
-In case of an development environment, create a virtual environment for your Python dependencies:
-
-```shell
-python3.8 -m venv python
-```
-
-No worries, the resulting `python` directory is excluded from the git respostory.
-
-To activate that environment, run
-
-```shell
-source python/bin/activate
-```
-
-Then, install the required dependencies
-
+Install dependencies:
 ```shell
-pip install -r requirements.txt
+apt install \
+    python3-flask \
+    python3-flask-sqlalchemy \
+    python3-http-parser \
+    python3-psycopg2 \
+    python3-requests \
+    python3-sqlalchemy \
+    python3-validators
 ```
 
 Create your base configuration from the sample configuration
@@ -80,8 +70,6 @@ cp config/sample-production.engine.ini config/engine.ini
 Engine requires a PorstgreSQL database to cache any programme info locally:
 
 ```bash
-# Additional Python packages for PostgreSQL
-pip3 install -r contrib/postgresql-requirements.txt
 # Create database and user (change password in script)
 sudo -u postgres psql -f contrib/postgresql-create-database.sql
 ```
@@ -106,13 +94,7 @@ Required modifications are:
 
 ## Running Engine
 
-If you have defined a virtual env during the installation step you'll need to activate it first. You'll have to do so whenever you gonna start your development environment:
-
-```shell
-source python/bin/activate
-```
-
-There's a convenience script `run.sh` to get Engine components started.
+There's a convencience script `run.sh` to get engine started
 
 ```shell
 engine$ ./run.sh