Camera di stazione: acquisizione dal frontend e campi admin (#72)

Route POST /measure/api/vision/grab (proxy verso il servizio camera),
get_station_by_code, pulsante «Acquisisci dalla camera», grab() in
vision_execute.js, campi camera_url e camera_source nell'admin stazioni,
traduzioni it/en, extra_hosts host.docker.internal nel compose di sviluppo.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/frontend/flask_app/static/js/vision_execute.js

@@ -18,6 +18,7 @@ function visionExecute() {
 
   return {
     busy: false,
+    grabbing: false,   // frame requested from the station camera (#72)
     error: '',
     result: null,      // last execute response
     imageSrc: '',      // object URL of the acquired image (shown under the overlay)
@@ -61,6 +62,34 @@ function visionExecute() {
       }
     },
 
+    // Station camera (#72): the Flask proxy answers a PNG, which goes through
+    // acquire() like a picked file. Errors show as the execute ones do.
+    async grab() {
+      const cfg = window.__visionCfg || {};
+      if (this.busy || this.grabbing || !cfg.grabUrl) return;
+      this.grabbing = true;
+      this.error = '';
+      let blob = null;
+      try {
+        const csrf = document.querySelector('meta[name=csrf-token]')?.content || '';
+        const resp = await fetch(cfg.grabUrl, {
+          method: 'POST', headers: { 'X-CSRFToken': csrf },
+        });
+        if (!resp.ok) {
+          const body = await resp.json().catch(() => ({}));
+          this.error = body.detail || (cfg.labels && cfg.labels.requestFailed) || 'Error';
+          return;
+        }
+        blob = await resp.blob();
+      } catch (e) {
+        this.error = (cfg.labels && cfg.labels.requestFailed) || 'Error';
+        return;
+      } finally {
+        this.grabbing = false;
+      }
+      if (blob) await this.acquire(blob);
+    },
+
     // Input change: take the file and allow picking the same one again.
     onPick(ev) {
       const f = ev.target.files && ev.target.files[0];