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/init_defaults.py

@@ -3,10 +3,22 @@ import os
 from dotenv import load_dotenv
 import bcrypt
 
-# .env laden
-load_dotenv()
+# .env laden (nur in Dev)
+if os.getenv("ENV", "development") == "development":
+    load_dotenv()
 
-DB_URL = f"mysql+pymysql://{os.getenv('DB_USER')}:{os.getenv('DB_PASSWORD')}@{os.getenv('DB_HOST')}:3306/{os.getenv('DB_NAME')}"
+# Use same logic as database.py: prefer DB_CONN, fallback to individual vars
+DB_URL = os.getenv("DB_CONN")
+if not DB_URL:
+    DB_USER = os.getenv("DB_USER", "infoscreen_admin")
+    DB_PASSWORD = os.getenv("DB_PASSWORD")
+    # In Docker Compose: DB_HOST will be 'db' from env
+    # In dev container: will be 'localhost' from .env
+    DB_HOST = os.getenv("DB_HOST", "db")  # Default to 'db' for Docker Compose
+    DB_NAME = os.getenv("DB_NAME", "infoscreen_by_taa")
+    DB_URL = f"mysql+pymysql://{DB_USER}:{DB_PASSWORD}@{DB_HOST}:3306/{DB_NAME}"
+
+print(f"init_defaults.py connecting to: {DB_URL.split('@')[1] if '@' in DB_URL else DB_URL}")
 engine = create_engine(DB_URL, isolation_level="AUTOCOMMIT")
 
 with engine.connect() as conn:
@@ -53,6 +65,7 @@ with engine.connect() as conn:
             ('video_autoplay', 'true', 'Autoplay (automatisches Abspielen) für Videos'),
             ('video_loop', 'true', 'Loop (Wiederholung) für Videos'),
             ('video_volume', '0.8', 'Standard Lautstärke für Videos (0.0 - 1.0)'),
+            ('holiday_banner_enabled', 'true', 'Ferienstatus-Banner auf Dashboard anzeigen'),
         ]
     
         for key, value, description in default_settings: