feat(api): POST /api/v1/aider/events HMAC webhook + Redis stream push

- Router layer: HTTP validation + HMAC-SHA256 signature verification
- Service layer: Redis stream push (aider_event_service.push_aider_batch_to_stream)
- leWOOOgo積木化遵循: Router → Service → Redis
- All 6 tests passing (signature validation, batch limits, edge cases)

apps/api/src/services/aider_event_service.py

@@ -5,10 +5,12 @@
 - 不重做 dedup — 既有 IncidentService.create_incident_from_signal 已有 3min fingerprint debounce
 - 不做 pattern extract — Task A8 ai_router 會直接從 aider_event_repository 聚合
 - 純函式為主，副作用（建 incident）由 caller（A7 processor job）管理
+- Redis stream 推送 (Task A6)：轉接 Router 層
 """
 from __future__ import annotations
+import os
 from typing import Any
-from src.models.aider import AiderEventIn
+from src.models.aider import AiderEventIn, AiderBatchIn
 from src.utils.secret_redactor import redact
 
 
@@ -109,3 +111,25 @@ def _compact_desc(event_type: str, payload: dict) -> str:
                 f"duration={payload.get('duration_sec',0)}s "
                 f"tokens={payload.get('tokens_sent',0)}+{payload.get('tokens_received',0)}")
     return str(payload)[:200]
+
+
+# ---- Redis stream 推送 (Task A6) ----
+
+async def push_aider_batch_to_stream(batch: AiderBatchIn) -> list[str]:
+    """把 event batch 推到 Redis stream。回傳 stream ID 列表。"""
+    from src.core.redis_client import get_redis
+
+    stream_key = os.environ.get("AIDER_EVENTS_STREAM_KEY", "signals:aider:events")
+    r = get_redis()
+
+    ids = []
+    for ev in batch.events:
+        msg_id = await r.xadd(stream_key, {"payload": ev.model_dump_json()})
+        ids.append(_to_str(msg_id))
+
+    return ids
+
+
+def _to_str(x) -> str:
+    """轉成 str（相容 bytes 和 str 回傳值）。"""
+    return x.decode() if isinstance(x, bytes) else str(x)