docs/dev: sync backend rework, MQTT, and devcontainer hygiene

README: add Versioning (unified SemVer, pre-releases, build metadata); emphasize UTC handling and streaming endpoint; add Dev Container notes (UI-only Remote Containers, npm ci, idempotent aliases)
TECH-CHANGELOG: backend rework notes (serialization camelCase, UTC normalization, streaming metadata); add component build metadata template (image tags/SHAs)
Copilot instructions: integrate maintenance guardrails; reinforce UTC and camelCase conventions; document MQTT topics and scheduler retained payload behavior
Devcontainer: map Remote Containers to UI; remove in-container install; switch to npm ci; make aliases idempotent

server/Dockerfile.dev

@@ -9,7 +9,7 @@ FROM python:3.13-slim
 # verbindet (gemäß devcontainer.json). Sie schaden aber nicht.
 ARG USER_ID=1000
 ARG GROUP_ID=1000
-RUN apt-get update && apt-get install -y --no-install-recommends locales curl git \
+RUN apt-get update && apt-get install -y --no-install-recommends locales curl git docker.io \
     && groupadd -g ${GROUP_ID} infoscreen_taa \
     && useradd -u ${USER_ID} -g ${GROUP_ID} --shell /bin/bash --create-home infoscreen_taa \
     && sed -i 's/# de_DE.UTF-8 UTF-8/de_DE.UTF-8 UTF-8/' /etc/locale.gen \