Security: Add .gitignore, remove sensitive files from tracking

- Added comprehensive .gitignore for secrets, tokens, session data
- Untracked openclaw.json (contains API tokens)
- Untracked device-auth.json, paired.json
- Untracked session .jsonl files (conversation history)
- Untracked cron run logs

Note: Files still exist locally, just no longer version controlled

cron/runs/6f19d187-7dd1-4409-af62-8f7d2bce6d7c.jsonl

@@ -1 +0,0 @@
-{"ts":1770303600023,"jobId":"6f19d187-7dd1-4409-af62-8f7d2bce6d7c","action":"finished","status":"ok","summary":"Run session_status to show current model usage, token consumption, and costs. Provide a brief summary of usage trends if notable.","runAtMs":1770303600021,"durationMs":0,"nextRunAtMs":1770390000000}

cron/runs/77e0c1fa-1a84-4bd0-850b-62c5a8f8a59e.jsonl

@@ -1 +0,0 @@
-{"ts":1770303600020,"jobId":"77e0c1fa-1a84-4bd0-850b-62c5a8f8a59e","action":"finished","status":"ok","summary":"Get the current weather for Denver using Open-Meteo API (latitude=39.74, longitude=-104.99). Use exec with curl to fetch: https://api.open-meteo.com/v1/forecast?latitude=39.74&longitude=-104.99&current_weather=true&temperature_unit=fahrenheit — Parse the JSON and provide a concise morning weather summary.","runAtMs":1770303600006,"durationMs":8,"nextRunAtMs":1770390000000}