fix(lint): resolve ruff 0.16 DTZ007/BLE001 failures blocking CI

CI installs unpinned latest ruff; 0.16.0 flags two pre-existing lines,
failing ci / ci on every PR (including safe Dependabot bumps #31/#32).

- sla_monitor: parse START_DATE with date.fromisoformat() instead of a
  naive strptime().date() round-trip (identical result, no naive datetime)
- user_sync: keep the deliberate per-user blanket catch (one failed update
  must not abort the sync) with a justified noqa: BLE001

src/sla_monitor/app.py

@@ -2,7 +2,7 @@ import json
 import logging
 import os
 import time
-from datetime import datetime, timedelta, timezone
+from datetime import date, datetime, timedelta, timezone
 from urllib import error, parse, request
 from zoneinfo import ZoneInfo
 
@@ -366,7 +366,7 @@ def handler(event, context):
     now_et = now.astimezone(EASTERN)
 
     if start_date:
-        start = datetime.strptime(start_date, "%Y-%m-%d").date()
+        start = date.fromisoformat(start_date)
         if now_et.date() < start:
             logger.info("Before start date %s, skipping", start_date)
             return {"skipped": True, "reason": "before_start_date"}

src/user_sync/app.py

@@ -191,7 +191,7 @@ def handler(event, context):
                 logger.info("Skipped %s - not a Front teammate", email)
                 summary["not_in_front"] += 1
 
-        except Exception as e:
+        except Exception as e:  # noqa: BLE001 - per-user isolation: one failed update must not abort the sync
             logger.error("Error updating %s: %s", email, e)
             summary["errors"] += 1
             summary["error_details"].append({"email": email, "message": str(e)})