Rename brewpi/ to server/

Pure rename (brewpi.py, brewpi.sh, requirements.txt, __init__.py) plus
the README's path references - no code changes. "server/" describes
the directory's role rather than duplicating the project name already
in brewpi.py itself.

README.md

@@ -14,7 +14,7 @@ backends for an induction hob and an RTD temperature probe.
 ## Architecture
 
 ```
-brewpi/brewpi.py            Server entry point: wires sensor, pot/plant,
+server/brewpi.py            Server entry point: wires sensor, pot/plant,
                              heater, temperature controller and stirrer
                              together, runs them as asyncio tasks, and
                              serves state/commands over a WebSocket.
@@ -74,7 +74,7 @@ config.json.sim               Configuration template for simulation mode.
 
 ### Data flow
 
-The server (`brewpi/brewpi.py`) loads `config.json`, builds the configured
+The server (`server/brewpi.py`) loads `config.json`, builds the configured
 sensor/heater/stirrer/controller via factories (`*Factory.create(name, ...)`)
 based on the `Controller` section (`sensor_name`, `heater_name`,
 `stirrer_name`, `pid_type`, or `"sim"` for any of them), and connects their
@@ -92,14 +92,14 @@ commands back on (e.g. `{"TempCtrl": {"Soll": {"Temp": 65}}}`).
 ## Requirements
 
 - Python 3.8+
-- Server (`brewpi/requirements.txt`): `numpy`, `scipy`, `websockets`, `dpath`,
+- Server (`server/requirements.txt`): `numpy`, `scipy`, `websockets`, `dpath`,
   and `pyserial`/`spidev` if using real hardware backends.
 - Client (`client/requirements.txt`): `PyQt5`.
 
 Install with:
 
 ```bash
-pip install -r brewpi/requirements.txt
+pip install -r server/requirements.txt
 pip install -r client/requirements.txt
 ```
 
@@ -112,7 +112,7 @@ pip install -r client/requirements.txt
 2. Start the server:
 
    ```bash
-   cd brewpi
+   cd server
    ./brewpi.py
    ```
 
@@ -124,7 +124,7 @@ pip install -r client/requirements.txt
    ./brewpi_gui.py
    ```
 
-`brewpi/brewpi.sh` shows how this is wired up to run under a `virtualenvwrapper`
+`server/brewpi.sh` shows how this is wired up to run under a `virtualenvwrapper`
 environment (`$WORKON_HOME`/`$BREWPI_HOME`) on a Raspberry Pi-style deployment.
 
 ## Mash schedules