Fix GET /mcp 405 log spam and resolve_account email matching

Add a custom GET /mcp health route so health checks and client polling
return 200 instead of flooding logs with 405. Also allow resolve_account
to match by email address (from_address, imap_username, smtp_username)
in addition to account ID.

src/server.py

@@ -117,6 +117,14 @@ def resolve_account(accounts: list[dict], account_id: Optional[str] = None) -> d
     for acc in accounts:
         if acc["id"] == account_id:
             return acc
+    # Fallback: match by email address (from_address, imap_username, smtp_username)
+    for acc in accounts:
+        if account_id in (
+            acc.get("from_address"),
+            acc.get("imap_username"),
+            acc.get("smtp_username"),
+        ):
+            return acc
     raise ValueError(
         f"Unknown account_id: {account_id}. Available: {[a['id'] for a in accounts]}"
     )
@@ -493,6 +501,13 @@ if not mcp_api_key:
 mcp = FastMCP("poke-mail", lifespan=lifespan, auth=auth)
 
 
+@mcp.custom_route("/mcp", methods=["GET"])
+async def health(request):
+    from starlette.responses import JSONResponse
+
+    return JSONResponse({"status": "ok"})
+
+
 @mcp.tool(
     description="Search emails by criteria. Returns a list of matching emails with metadata."
 )