chore(branding): point firmware at wevisto.com

Flip APP_BASE_URL and the on-screen "go to <domain>/setup/..." text in
the rendered setup_bg images from pictureframe.edholm.me to wevisto.com.
Per the dual-domain migration plan (Option C — server keeps both alive
indefinitely), this only affects newly-flashed units; field devices on
the old URL keep working against the same backend.

Regenerated both panels' setup_bg.bin via gen_screens*.py so the
embedded URL in the on-screen QR overlay text matches the firmware's
runtime poll URL.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/mocks/config.h

@@ -1,7 +1,7 @@
 #pragma once
 // Mirror of src/config.h for use in native unit tests.
 // Values must match src/config.h so test assertions stay consistent.
-#define APP_BASE_URL      "https://pictureframe.edholm.me"
+#define APP_BASE_URL      "https://wevisto.com"
 #define NVS_NAMESPACE     "pf"
 #define NVS_KEY_SSID        "ssid"
 #define NVS_KEY_PASS        "pass"