fix(sprint3): 首席架構師 Review C1/C2/C3/M3/m1 修正

C1: _ssh_execute 直接接收 key_path 參數，不反查 LAYER_SSH_CONFIG
C2: PlaybookService.create() proxy，Router 不再穿透呼叫 _repository
C3: CD Step 1b sed 替換 IMAGE_TAG_PLACEHOLDER，消除失敗中斷風險
M3: repair-bot 110/188 regex 統一 [a-z0-9][a-z0-9-]{0,30}，禁止底線
m1: defaultMode 0400 加八進位說明注釋
m2: _ssh_execute 用 deadline 計算剩餘 timeout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/services/host_repair_agent.py

@@ -2,11 +2,12 @@
 src/services/host_repair_agent.py
 Host Repair Agent — 透過 SSH 執行主機層修復
 2026-04-05 Claude Code: Sprint 3 Host Auto-Repair
+2026-04-05 Claude Code: C1 修正 — key_path 直接傳入 _ssh_execute，不反查
 """
 import asyncio
 import re
 import logging
-from dataclasses import dataclass, field
+from dataclasses import dataclass
 
 logger = logging.getLogger(__name__)
 
@@ -81,6 +82,7 @@ class HostRepairAgent:
             output = await self._ssh_execute(
                 host=config["host"],
                 user=config["user"],
+                key_path=config["key_path"],
                 command=command,
             )
         except asyncio.TimeoutError:
@@ -107,13 +109,10 @@ class HostRepairAgent:
             error="" if success else output,
         )
 
-    async def _ssh_execute(self, host: str, user: str, command: str) -> str:
-        """執行 SSH 命令，回傳 stdout。"""
-        key_path = LAYER_SSH_CONFIG.get(
-            next((k for k, v in LAYER_SSH_CONFIG.items() if v["host"] == host and v["user"] == user), None),
-            {}
-        ).get("key_path", "/etc/repair-ssh/id_ed25519")
-
+    async def _ssh_execute(self, host: str, user: str, key_path: str, command: str) -> str:
+        """執行 SSH 命令，回傳 stdout。key_path 由呼叫方傳入，不反查。"""
+        import time
+        deadline = time.monotonic() + SSH_TIMEOUT
         proc = await asyncio.wait_for(
             asyncio.create_subprocess_exec(
                 "ssh",
@@ -128,7 +127,8 @@ class HostRepairAgent:
             ),
             timeout=SSH_TIMEOUT,
         )
-        stdout, stderr = await asyncio.wait_for(proc.communicate(), timeout=SSH_TIMEOUT)
+        remaining = max(1.0, deadline - time.monotonic())
+        stdout, stderr = await asyncio.wait_for(proc.communicate(), timeout=remaining)
         output = stdout.decode().strip()
         logger.info("SSH repair %s@%s %s → %s", user, host, command, output)
         return output