Add workspace_id support for multi-workspace tracking

[saint0x]

Summary

This PR adds workspace ID support throughout the system to enable multi-workspace tracking and data isolation. The workspace ID is now extracted from the auth response, propagated through the event processing pipeline, and stored in all ClickHouse tables alongside the project ID.

Key Changes

• Auth Layer: Added workspace_id field to AuthContext and AuthResponse structs with extraction logic and mock generation
• Event Processing: Updated ClickHouseEvent::from_sdk() to accept and store workspace ID, modified transform_batch() to pass workspace ID through the transformation pipeline
• ClickHouse Schema: Added workspace_id column to all event and metric tables (events, sessions, pageviews, clicks, scroll_events, mouse_moves, form_events, errors, performance_metrics, visibility_events, resource_loads, geographic, custom_events)
• Query Layer: Updated SELECT queries to include workspace_id field in result rows
• Index Optimization: Updated ORDER BY clauses in all tables to include workspace_id for better query performance with multi-workspace filtering
• Testing: Added test fixtures and mock implementations to generate deterministic workspace IDs, updated existing tests to verify workspace_id propagation

Implementation Details

• Workspace ID is generated deterministically in the mock auth client using a hash of the API key (similar to project ID generation)
• The workspace ID flows through the entire event pipeline: auth → extraction → transformation → ClickHouse insertion
• All ClickHouse table schemas have been updated to include workspace_id as a primary dimension for partitioning and ordering
• The implementation maintains backward compatibility with existing project_id-based filtering while adding workspace-level isolation