feat: Beta Features System - Feature flags with config registry + DB state

[filipexyz]

Summary

Implement a beta features system that allows developers to define experimental features in a config file and users to toggle them on/off via the Settings UI.

Motivation

We need a way to:

• Ship experimental features without exposing them to all users by default
• Let users opt-in to try beta functionality
• Gate entire UI sections behind feature flags
• Track which features are enabled without code changes

Design

Hybrid Config + Database approach:

Component	Purpose
beta-features.toml	Defines available features (name, description, maturity) - version controlled
forge_beta_feature_state table	Stores user's enabled/disabled preferences
Settings UI	"Beta Features" tab with toggles
<BetaFeatureGate>	React component for conditional rendering

Developer Workflow

1. Add feature to beta-features.toml:

[features.my_feature]
name = "My Feature"
description = "What it does"
maturity = "experimental"

2. Use in code:

// Backend
if services.beta_features.is_enabled("my_feature").await? { ... }

// Frontend
<BetaFeatureGate feature="my_feature">
  <MyFeatureComponent />
</BetaFeatureGate>

Acceptance Criteria

• Config file (beta-features.toml) for feature definitions
• Database table for enabled/disabled state
• Rust service with is_enabled() check
• API endpoints: GET /api/forge/beta-features, POST .../toggle
• React context with useBetaFeature() hook
• <BetaFeatureGate> component for UI gating
• Settings page with feature toggles
• TypeScript types auto-generated