v2.0.3: Improve error handling, add tests, cleanup

- Fix bare except clauses in curator.py and main.py
- Change embedding model to snowflake-arctic-embed2
- Increase semantic_score_threshold to 0.6
- Add memory context explanation to systemprompt.md
- Add pytest dependencies to requirements.txt
- Remove unused context_handler.py and .env.example
- Add project documentation (CLAUDE.md) and test files

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

app/curator.py

@@ -171,7 +171,8 @@ Remember: Respond with ONLY valid JSON. No markdown, no explanations, just the J
             mem_time = datetime.fromisoformat(timestamp.replace("Z", "+00:00"))
             cutoff = datetime.utcnow() - timedelta(hours=hours)
             return mem_time.replace(tzinfo=None) > cutoff
-        except:
+        except (ValueError, TypeError):
+            logger.debug(f"Could not parse timestamp: {timestamp}")
             return True
 
     def _format_raw_turns(self, turns: List[Dict]) -> str: