Add AI storyboard studio for Director workflow

[pat3dx]

Summary

This PR adds an AI-assisted storyboard workflow to Camera Lab's Director UI while keeping the existing manual storyboard import path intact.

Highlights

• Adds an AI provider settings modal for OpenRouter and Kie API configuration.
• Adds an AI Studio section inside Storyboard Import.
• Supports creative reference image upload or public image URL override.
• Generates shot scripts with OpenRouter.
• Generates storyboard panel images with Kie Nano Banana 2.
• Generates LTX 2.3-ready per-shot prompts.
• Expands storyboard import to 2x2, 3x3, and 4x4.
• Adds Nano Banana 2 controls for aspect ratio, resolution, and output format.
• Hides long result prompt text in output cards.
• Adds animated running state for result cards.
• Fixes non-16:9 preview sizing.
• Fixes startup when the repo path contains spaces.
• Ignores .camera_lab_ai_settings.json so provider keys are not committed.

Validation

• python -m py_compile server/camera_lab_server.py
• node --check frontend/app.js
• git diff --check
• Local end-to-end test through AI storyboard generation, timeline import, and LTX Director video generation.
• Secret scan confirmed no literal provider keys are in the committed diff.

[ai2764]

Hi, I'm working on upgrading the LTX director workflow to version 2. https://github.com/WhatDreamsCost/WhatDreamsCost-ComfyUI
There might be a lot of changes on my side. And some of the existing features may no longer applicable. I would love to go through your proposed features after v2 is integrated.