[Serpentcrest] K9 Job Spawns + Door Fix (#5883)

## Short description
<!-- What do you propose to change with your PR? -->
Adds 2 K9 Spawn, Water Cooler for water and a pet carrier also updates
metadata for Serpentcrest to new engine also changes Sec front doors to
Brig access to allow Cadets to enter
## Why we need to add this
<!-- What is the reason for adding these changes? Please post links to
Discussions as well as Bug Reports here. Please describe how this will
change the game balance. -->
Apart of mapping chore:
#5821 
## Media (Video/Screenshots)
<!--
If your PR contains in-game changes you must provide screenshots/videos
of the changes.
-->
Pet Beds + Water Cooler:
<img width="380" height="258" alt="Screenshot 2026-08-30 172647"
src="https://github.com/user-attachments/assets/7a418981-01b0-4ad2-adb8-5d0637497515"
/>


Pet Carrier:
<img width="387" height="312" alt="image"
src="https://github.com/user-attachments/assets/59b3f79e-3806-4ee7-bd18-fdb01ba16c8a"
/>

New Airlocks:
<img width="480" height="173" alt="image"
src="https://github.com/user-attachments/assets/1d56d54a-9cc8-4202-b673-00e3d76adf3d"
/>

## Checks
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- [x] I do not require assistance to complete the PR.
- [x] Before posting/requesting review of a PR, I have verified that the
changes work.
- [x] I have added screenshots/videos of the changes, or this PR does
not change in-game mechanics.
- [x] I affirm that my changes are licensed under the [MIT
License](https://github.com/ss14Starlight/space-station-14/blob/Starlight/LICENSE.TXT)
and grant permission for use in this repository under its conditions.

**Changelog**
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them using the template outside the comment. Short and informative. -->

:cl: Forrestgod
- add: [Serpentcrest] Added 2 K9 Spawn Slots in Security.
- add: [Serpentcrest] Added a water cooler in Security.
- add: [Serpentcrest] Added a Pet Carrier in Security.
- fix: [Serpentcrest] Sec front is now brig access, cadets allowed in
now.

Author: Forrestgod718