add Flask app (hello, frage, pinnwand)

app/.gitignore

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+venv/
+__pycache__/
+*.pyc

app/app.py

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+from flask import Flask, request, redirect
+
+app = Flask(__name__)
+
+@app.route("/")
+def hello():
+    return "Hallo aus meiner Flask-App!"
+
+@app.route("/frage", methods=["GET", "POST"])
+def frage():
+    if request.method == "POST":
+        if request.form.get("antwort") == "8":
+            return "Richtig!"
+        return "Leider falsch."
+    return '<form method="post">Was ist 3 + 5? ' \
+           '<input name="antwort"><button>OK</button></form>'
+
+# Pinnwand (in-memory)
+eintraege = []
+
+@app.route("/pinnwand", methods=["GET", "POST"])
+def pinnwand():
+    if request.method == "POST":
+        nachricht = request.form.get("nachricht", "").strip()
+        if nachricht:
+            eintraege.append(nachricht)
+        return redirect("/app/pinnwand")
+    liste = ""
+    for e in eintraege:
+        liste = liste + "<li>" + e + "</li>"
+    return '<h1>Pinnwand</h1>' \
+           '<form method="post"><input name="nachricht">' \
+           '<button>Senden</button></form><ul>' + liste + '</ul>'
+
+if __name__ == "__main__":
+    # Assuming room number 04 based on home directory isa4 -> port 9004
+    app.run(host="0.0.0.0", port=9004)