Optimize UI CPU usage

[Gold856]

Description

The big change here is to remove the loading SVG from the DOM and to stuff it into an <img> like before. This mostly restores the old CPU usage back down to the baseline of ~10% on my laptop. This also fixes the JSON.stringify hack used to check if the current camera settings was PlaceholderCameraSettings by using Object.freeze (this apparently allows normal equality operators to be used). This also takes CPU usage down a few extra percent. One dynamically calculated class was also removed because those are also CPU-expensive (and this instance was completely unnecessary and easy to remove. Doesn't have much impact though.)

Meta

Merge checklist:

• Pull Request title is short, imperative summary of proposed changes
• The description documents the what and why
• If this PR changes behavior or adds a feature, user documentation is updated
• If this PR touches photon-serde, all messages have been regenerated and hashes have not changed unexpectedly
• If this PR touches configuration, this is backwards compatible with settings back to v2025.3.2
• If this PR touches pipeline settings or anything related to data exchange, the frontend typing is updated
• If this PR addresses a bug, a regression test for it is added

[samfreund]

Is the goal here to optimize CPU usage on the client or the coprocessor?

[Gold856]

On the client.