Increase maximum depth for quick-select to 16

[philippotto]

URL of deployed dev instance (used for testing):

• https://___.webknossos.xyz

Steps to test:

• use depth=16 with ai quick select

TODOs:

• unify constant

Issues:

• follow-up for Integrate SAM 2 with 3D support #7990

---

(Please delete unneeded items, merge only when none are left open)

• Updated changelog
• Updated migration guide if applicable
• Updated documentation if applicable
• Adapted wk-libs python client if relevant API parts change
• Removed dev-only changes like prints and application.conf edits
• Considered common edge cases
• Needs datastore update after deployment

[fm3]

Backend LGTM