fix: detect Cloudflare challenge on HTTP 200 responses

Some anti-bot challenge pages return HTTP 200 instead of 403/503,
bypassing the FS fallback. Read response body on 200, check for
challenge indicators, and fall through to FlareSolverr if detected.

internal/httpclient/client.go

@@ -120,10 +120,32 @@ func (c *Client) Do(req *http.Request) (*http.Response, error) {
 	var directStatus int
 	if err == nil {
 		directStatus = resp.StatusCode
-		if resp.StatusCode != http.StatusForbidden && resp.StatusCode != http.StatusServiceUnavailable {
+		// Some Cloudflare challenge pages return HTTP 200 but contain challenge
+		// JavaScript. Check for challenge content on any response.
+		if resp.StatusCode == http.StatusOK {
+			body, readErr := io.ReadAll(io.LimitReader(resp.Body, 32*1024))
+			resp.Body.Close()
+			if readErr == nil && len(body) > 0 {
+				if isCloudflareChallenge(body) {
+					directStatus = http.StatusForbidden
+				} else {
+					// Not a challenge — wrap body and return
+					return &http.Response{
+						StatusCode:    resp.StatusCode,
+						Header:        resp.Header,
+						Body:          io.NopCloser(bytes.NewReader(body)),
+						ContentLength: int64(len(body)),
+						Request:       req,
+					}, nil
+				}
+			} else {
+				return resp, nil
+			}
+		} else if resp.StatusCode != http.StatusForbidden && resp.StatusCode != http.StatusServiceUnavailable {
 			return resp, nil
+		} else {
+			resp.Body.Close()
 		}
-		resp.Body.Close()
 	}
 
 	if c.fsClient == nil {