Replace numeric incremental ID with UUID or slug

Instead of using numeric incremental id for /prompts/{id} and /workflows/{id}, we can migrate to use either UUID (snowflakes or UUIDv4) or slug name (parsed from the prompt or workflow title)

For example:
/workflows/db053fdb-83c3-433b-81e4-3dec91a8eab6

or

/workflows/tatarot-2-past-reading-v4

Objective:

1. To support the feature of "Only accessible by link" when user want to share their prompt/workflow to a specific group of people, just like Google docs, etc.

2. Prevent bot scrapping or bot attack (since querying by numeric id will still let backend to check user credentials which increase server load when the attack volume is high)

3. Future proof for the prompt/workflow marketplace feature