Adds Client::uploadImage() for the Image API, matching upload_image in serpapi-ruby (#27) and serpapi-python (#38), and uploadImage in serpapi-javascript (#46).

$client = new Client(getenv('SERPAPI_KEY'));
$upload = $client->uploadImage('path/to/image.jpg');

$results = $client->search([
  'engine' => 'google_lens',
  'image_id' => $upload->image_id,
]);

Behavior

• Input: a file path or an open stream, such as fopen($path, 'rb') or php://memory.
  • Seekable streams are rewound first, as in Ruby.
  • Streams are uploaded from a temporary copy, because cURL uploads by path and CURLStringFile needs PHP 8.1.
• Request: a multipart/form-data POST to /image.
  • It carries the same parameters as any other request (api_key, source, default search parameters), the way Ruby's post reuses query(params).
  • The parameters go in the body, so the API key stays out of the URL.
  • Per-call api_key and timeout work as they do for search(), and null drops a default.
• File name: only the base name is sent. Without one, cURL would send the full local path.
• Return value: the decoded response as an object (message, image_id).
• Errors: a 400 such as "Invalid image format…" or a 401 raises SerpApiException with the same context as a search error, without the key or the file.

Fixes needed in the shared cURL handle

• Method reset: a GET on the persistent handle now sets CURLOPT_HTTPGET. Without it, the search that follows an upload goes out as a multipart POST. I confirmed both before and after the fix against a local echo server.
• Expect header: uploads send Expect: to drop Expect: 100-continue. libcurl before 7.69 adds that header to bodies over 1 KB, SerpApi doesn't answer it, and each upload stalled for about 1 s. I measured this by forcing the header against the live API.

request() gains an optional $form argument. It is @internal, and the test double RecordingClient was updated to match. The JSON parse error now reads "from url" instead of "on get url", as Ruby's does and as the HTTP error already did.

Tests

• ClientUploadImageTest (offline) covers:
  • path upload: endpoint, form fields, base name and a clean URL;
  • stream upload: rewind, temp copy deleted, caller's stream left open;
  • the same parameters as a search, including defaults and booleans;
  • per-call api_key, timeout and null;
  • API errors, missing key, missing file and invalid argument.
• ClientIntegrationTest::testUploadImage (live) uploads tests/fixtures/mona-lisa.jpg (a 27 KB public domain thumbnail from Wikimedia Commons). It then runs a Google Lens search for visual_matches on the same persistent connection.

Locally on PHP 8.5:

• the full suite passes offline: 116 tests;
• ClientIntegrationTest and the Google Lens example pass live;
• phpcs and PHPStan level 6 are clean.

A live stream upload also succeeded, and an invalid file returns the API's error message.

Follow-ups (not in this PR)

• Version bump: bump VERSION to 1.1.0 with a change log entry that includes this method. This replaces Bump version to 1.1.0 #6, which targets the merged feature/ruby-parity branch and lists Markdown as new, although Markdown is already in 1.0.0.
• release.yml: it passes API_KEY, but the tests read SERPAPI_KEY since chore: rename API_KEY env var to SERPAPI_KEY #4, so the v1.0.0 release ran with every live test skipped.