Webcam: Buttons fuer Kamera-Aufloesung (VGA/SVGA)

Schaltet die ESP32-CAM-Aufloesung per Button um (VGA 640x480 = mehr FPS,
SVGA 800x600 = mehr Detail). Server proxyt den /control-Aufruf an die
Kamera (Host automatisch aus CAMERA_URL, Port 80).

- /api/cam_framesize (Whitelist 10=VGA, 11=SVGA)
- zwei Buttons + Status-Feedback im Frontend

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app.py

@@ -6,6 +6,7 @@ import threading
 from datetime import datetime
 from zoneinfo import ZoneInfo
 from threading import Event, Lock, Condition
+from urllib.parse import urlparse
 
 import cv2
 import numpy as np
@@ -839,6 +840,38 @@ def grabber_toggle():
     return jsonify({"paused": paused})
 
 
+# Erlaubte framesize-Werte der ESP32-CAM (OV2640): Wert -> Label.
+FRAMESIZES = {10: "VGA 640x480", 11: "SVGA 800x600"}
+
+
+@app.route("/api/cam_framesize", methods=["POST"])
+def cam_framesize():
+    """Setzt die Aufloesung der ESP32-CAM ueber deren /control-Endpoint.
+    Der Server proxyt den Aufruf (Browser braucht keinen Direktzugriff)."""
+    data = request.get_json(silent=True) or {}
+    try:
+        val = int(data.get("val"))
+    except (TypeError, ValueError):
+        abort(400, description="val (int) erforderlich")
+    if val not in FRAMESIZES:
+        abort(400, description="nur 10 (VGA) oder 11 (SVGA)")
+
+    host = urlparse(CAMERA_URL).hostname
+    if not host:
+        abort(500, description="CAMERA_URL ohne gueltigen Host")
+
+    # Steuer-Endpoint liegt auf Port 80 (Stream laeuft separat auf :81).
+    ctrl_url = f"http://{host}/control?var=framesize&val={val}"
+    try:
+        r = requests.get(ctrl_url, timeout=5)
+        r.raise_for_status()
+    except requests.RequestException as exc:
+        print(f"[cam] framesize set failed: {exc}", flush=True)
+        return jsonify({"ok": False, "error": str(exc)}), 502
+    print(f"[cam] framesize -> {FRAMESIZES[val]}", flush=True)
+    return jsonify({"ok": True, "val": val, "label": FRAMESIZES[val]})
+
+
 @app.route("/api/reset_count", methods=["POST"])
 def reset_count():
     data = request.get_json(silent=True) or {}