The Tools Server hostname turned out to be Cloudflare-proxied, not a
direct connection to nginx -- so the ESP32 (and any browser) sees
Cloudflare's own edge certificate (issued by Google Trust Services),
never the Origin CA cert, which only ever sits on the Cloudflare-to-
origin leg. Confirmed on hardware: ESP_ERR_HTTP_CONNECT.
Tried switching to ESP-IDF's built-in public CA bundle instead
(esp_crt_bundle_attach) as the more general fix, but that also failed
on hardware ("No matching trusted root certificate found") -- the
bundle's copy of the relevant Google root has the same name and public
key as the live one but a different serial/signature (a reissue), and
the bundle does an exact byte-level match, not a semantic one.
Simplest reliable fix: embed the exact certificate the proxy actually
presents (extracted live via openssl s_client, see
firmware/main/certs/tools_server_ca.pem) and trust that directly via
cert_pem, sidestepping bundle-matching semantics entirely. Documented
in firmware/README.md how to re-extract if the proxy's CA ever changes.
