docs: add python/pixi/epics docs

docs/python/epics.md

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+# EPICS
+
+Where is EPICS Base (https://gitea.psi.ch/epics) installed?
+```
+echo $EPICS
+```
+
+Host architecture that EPICS Base runs on:
+```
+echo $EPICS_HOST_ARCH
+```
+
+Which channel access lib is being used in python?
+```
+[sls-vserv-bd-hla01-dev playground]$ python3 -c "import ctypes; import epics.ca; print(epics.ca.find_libca())"
+/usr/local/epics/base-7.0.9/lib/RHEL9-x86_64/libca.so
+```
+
+
+Example reading from a PV:
+```
+[sls-vserv-bd-hla01-dev ~]$ /bin/python
+Python 3.9.25 (main, Apr 17 2026, 00:00:00)
+[GCC 11.5.0 20240719 (Red Hat 11.5.0-14)] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> from epics import PV
+>>> pv = PV("AGEBD-PLAYGROUND-DEV:AO")
+>>> pv.get()
+5.0
+>>>
+```
+
+## System python installed packages
+
+```
+/bin/python -m pip list -v
+```
+
+## Systemd Services
+
+When ssh-ing into a machine, `/etc/profile.d/*` automatically gets sourced.
+
+When running a `systemd` service, this does not happen.
+
+That's why we need to source `/etc/profile.d/cas_12_epics.sh` in our startup script
+to make sure that `EPICS` is configured properly.

docs/python/pixi.md

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+# Pixi
+
+## Install
+
+```
+curl -fsSL https://pixi.sh/install.sh | sh
+```
+
+installs in `${HOME}/.pixi/bin`