Rebalance Spawnpoints

[legokidlogan]

Does some assorted cleanup to match current CFC coding standards (and fix minor bugs), adds some audiovisual polish for player interaction, and makes the following balance changes:

• Max spawnpoint count per player is now 1. (sbox_maxsent_spawnpoint)
• When a player spawns, they have a 10s cooldown before they can create/link spawnpoints. (cfc_spawnpoints_cooldown_on_ply_spawn)
• When a spawnpoint is created, it has a 5s cooldown before anyone can link to it. (cfc_spawnpoints_cooldown_on_point_spawn)
• Both cooldowns only apply if the player had another spawnpoint removed in the past 30s, so the system doesn't impede initial base setup.
  (cfc_spawnpoints_removal_window)

The goal is to make it considerably harder for someone to maintain a permanent spawn point by repeatedly creating and linking to one (or pre-spawned backups) between deaths. Now defenders must actually defeat any immediate threats before they can reclaim their spawn if it gets destroyed while they are still alive.