feat: add pipeline engine with approval flow and file triggers

Sequential step executor (script, claude_prompt, approval, api_call,
template, skyvern placeholder), reaction-based approvals, file upload
trigger matching, portal API state sync.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pipelines/steps/api_call.py

@@ -0,0 +1,33 @@
+"""API call step — make HTTP requests."""
+
+import logging
+
+import httpx
+
+logger = logging.getLogger(__name__)
+
+
+async def execute_api_call(config: dict, **_kwargs) -> str:
+    """Make an HTTP request and return the response body."""
+    url = config.get("url", "")
+    if not url:
+        raise ValueError("api_call step requires 'url' field")
+
+    method = config.get("method", "GET").upper()
+    headers = config.get("headers", {})
+    body = config.get("body")
+
+    async with httpx.AsyncClient(timeout=30.0) as client:
+        if method == "GET":
+            resp = await client.get(url, headers=headers)
+        elif method == "POST":
+            resp = await client.post(url, headers=headers, content=body)
+        elif method == "PUT":
+            resp = await client.put(url, headers=headers, content=body)
+        elif method == "DELETE":
+            resp = await client.delete(url, headers=headers)
+        else:
+            raise ValueError(f"Unsupported HTTP method: {method}")
+
+        resp.raise_for_status()
+        return resp.text