[Feature] Settings & Preferences - App-Wide Configuration and User Preferences

[vzeman]

Summary

Implement a comprehensive settings system covering general preferences, generation defaults, performance tuning, notifications, and advanced developer options. A well-designed settings system reduces friction and allows power users to tune behavior to their workflow.

Requirements

API Keys

The Settings screen must include a dedicated API Keys tab or section where users configure credentials for all external AI services. Without valid API keys, generation features are disabled.

Anthropic (Claude)

• API key input field (masked, show/hide toggle)
• Link to https://console.anthropic.com to get a key
• Validate key on save (make a lightweight test call)
• Connection status indicator: Connected / Invalid key / Not set
• Used for: Storytelling Agent, prompt enhancement, quality analysis, caption translation

Replicate

• API key input field (masked, show/hide toggle)
• Link to https://replicate.com/account/api-tokens to get a key
• Validate key on save
• Connection status indicator
• Used for: AI video generation, text-to-image generation

ElevenLabs

• API key input field (masked, show/hide toggle)
• Link to https://elevenlabs.io to get a key
• Validate key on save
• Connection status indicator
• Used for: Voice narration generation, voice cloning

Storage

• API keys must be stored securely using the platform keychain:
  • macOS: Keychain Access
  • iOS: iOS Keychain
  • Other: Encrypted local storage (AES-256)
• Keys are never stored in plain text or included in exported project files
• "Clear all API keys" button with confirmation dialog

UX Notes

• On first launch, if no API keys are set, show a setup banner/wizard guiding user to the Settings -> API Keys screen
• Each generation feature should show a clear error if the relevant API key is missing (not just fail silently)
• Test connection button per service

General

• Theme: Light, Dark, System
• Language (i18n support structure)
• Default project save location
• Auto-save interval

Generation Defaults

• Default video model
• Default image model
• Default voice
• Default resolution
• Default FPS
• Default quality preset

Performance

• Max concurrent generations (1-5)
• Cache size limit
• Temp file cleanup policy

Notifications

• Generation complete notification
• Error notifications
• Sound on complete

Privacy

• Analytics opt-in/out
• Crash reporting

Advanced

• Custom FFmpeg path
• Custom Replicate base URL (for proxies)
• Debug logging level
• Developer mode (show raw API responses)

Acceptance Criteria

• Theme switcher applies Light/Dark/System correctly
• Generation defaults apply to all new scenes
• Concurrent generation limit is enforced in the generation queue
• Notifications fire correctly on generation completion and errors
• Developer mode exposes raw API response panels

Related

Part of the ai-video-editor Flutter application. Settings used throughout the app, especially by #65 (Video Generation) and #61 (Project Management).