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/template.py

@@ -0,0 +1,18 @@
+"""Template step — format and post a message to the target room."""
+
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+async def execute_template(config: dict, send_text=None, target_room: str = "", **_kwargs) -> str:
+    """Render a template message and post it to the target room."""
+    template = config.get("template", config.get("message", ""))
+    if not template:
+        raise ValueError("template step requires 'template' or 'message' field")
+
+    # Template is already rendered by the engine before reaching here
+    if send_text and target_room:
+        await send_text(target_room, template)
+
+    return template