feat: add DBOS skills for TypeScript, Python, and Go (#94)

Add three DBOS SDK skills with reference documentation for building
reliable, fault-tolerant applications with durable workflows.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

skills/dbos-python/references/pattern-scheduled.md

@@ -0,0 +1,56 @@
+---
+title: Create Scheduled Workflows
+impact: MEDIUM
+impactDescription: Run workflows exactly once per time interval
+tags: scheduled, cron, recurring, timer
+---
+
+## Create Scheduled Workflows
+
+Use `@DBOS.scheduled` to run workflows on a schedule. Workflows run exactly once per interval.
+
+**Incorrect (manual scheduling):**
+
+```python
+# Don't use external cron or manual timers
+import schedule
+schedule.every(1).minute.do(my_task)
+```
+
+**Correct (DBOS scheduled workflow):**
+
+```python
+@DBOS.scheduled("* * * * *")  # Every minute
+@DBOS.workflow()
+def run_every_minute(scheduled_time, actual_time):
+    print(f"Running at {scheduled_time}")
+    do_maintenance_task()
+
+@DBOS.scheduled("0 */6 * * *")  # Every 6 hours
+@DBOS.workflow()
+def periodic_cleanup(scheduled_time, actual_time):
+    cleanup_old_records()
+```
+
+Scheduled workflow requirements:
+- Must have `@DBOS.scheduled` decorator with crontab syntax
+- Must accept two arguments: `scheduled_time` and `actual_time` (both `datetime`)
+- Main thread must stay alive for scheduled workflows
+
+For apps with only scheduled workflows (no HTTP server):
+
+```python
+import threading
+
+if __name__ == "__main__":
+    DBOS.launch()
+    threading.Event().wait()  # Block forever
+```
+
+Crontab format: `minute hour day month weekday`
+- `* * * * *` = every minute
+- `0 * * * *` = every hour
+- `0 0 * * *` = daily at midnight
+- `0 0 * * 0` = weekly on Sunday
+
+Reference: [Scheduled Workflows](https://docs.dbos.dev/python/tutorials/scheduled-workflows)