Move preset management to addon preferences

[Weisl]

Preset creation, editing, and deletion should be moved out of the main panel and into the addon Preferences window.

Rationale: Preset management is a setup/configuration task, not something users do during a normal export workflow. Keeping it in the main panel adds visual noise. Preferences is the natural home for managing reusable configurations.

Scope:

• Move the preset list (add / rename / delete / duplicate) to a dedicated tab or section in the addon preferences
• The main export panel should only allow selecting an existing preset per collection, not managing presets
• Pre-installed (locked) presets and user presets should both be visible in preferences with clear distinction