v1.1.0 development: Smart Loop + safer background capture

[Mr9satana]

Development PR for v1.1.0.

Current scope:

• automatic Smart Loop frame/motion matching near requested duration;
• background capture no longer parks the render window at -32000/-32000;
• black-frame validation before the main export;
• compatibility placement and visible-capture fallback instead of silently producing a black video;
• v1.1 dev version metadata and CI build.

Do not merge until runtime testing on the problematic admin PC is complete.

[Mr9satana]

v1.1 dev CI is green after fixing the initial compile errors. Windows self-contained artifact built successfully.

Test focus before merge:

• Scene/Web background export on the problematic admin PC;
• automatic black-frame detection and compatibility/visible fallback;
• Smart Loop natural boundary detection near the requested duration;
• audio on/off and direct Video wallpaper conversion.

Built artifact SHA-256: 495a1dd8ef6c1a0f58d05019aa2508a396710b68835273f6dc8db9a12bfce48c.

Keep PR in draft until runtime tests pass.