feat(config): Restructure .taskmasterconfig and enhance gateway integration

Config Structure Changes and Gateway Integration

## Configuration Structure Changes
- Restructured .taskmasterconfig to use 'account' section for user settings
- Moved userId, userEmail, mode, telemetryEnabled from global to account section
- API keys remain isolated in .env file (not accessible to AI)
- Enhanced getUserId() to always return value, never null (sets default '1234567890')

## Gateway Integration Enhancements
- Updated registerUserWithGateway() to accept both email and userId parameters
- Enhanced /auth/init endpoint integration for existing user validation
- API key updates automatically written to .env during registration process
- Improved user identification and validation flow

## Code Updates for New Structure
- Fixed config-manager.js getter functions for account section access
- Updated user-management.js to use config.account.userId/mode
- Modified telemetry-submission.js to read from account section
- Added getTelemetryEnabled() function with proper account section access
- Enhanced telemetry configuration reading with new structure

## Comprehensive Test Updates
- Updated integration tests (init-config.test.js) for new config structure
- Fixed unit tests (config-manager.test.js) with updated default config
- Updated telemetry tests (telemetry-submission.test.js) for account structure
- Added missing getTelemetryEnabled mock to ai-services-unified.test.js
- Fixed all test expectations to use config.account.* instead of config.global.*
- Removed references to deprecated config.subscription object

## Configuration Access Consistency
- Standardized configuration access patterns across entire codebase
- Clean separation: user settings in account, API keys in .env, models/global in respective sections
- All tests passing with new configuration structure
- Maintained backward compatibility during transition

Changes support enhanced telemetry system with proper user management and gateway integration while maintaining security through API key isolation.

.cursor/rules/ai_providers.mdc

@@ -50,6 +50,7 @@ This rule guides AI assistants on how to view, configure, and interact with the
     -   **Key Locations** (See [`dev_workflow.mdc`](mdc:.cursor/rules/dev_workflow.mdc) - Configuration Management):
         -   **MCP/Cursor:** Set keys in the `env` section of `.cursor/mcp.json`.
         -   **CLI:** Set keys in a `.env` file in the project root.
+        - As the AI agent, you do not have access to read the .env -- but do not attempt to recreate it!
     -   **Provider List & Keys:**
         -   **`anthropic`**: Requires `ANTHROPIC_API_KEY`.
         -   **`google`**: Requires `GOOGLE_API_KEY`.