feat(metabase): add Metabase integration

[AggManik]

Summary

Adds Metabase integration with API key auth, scheduled activity sync, and 14 MCP tools.

• Auth — API key with two fields: metabase_url + api_key (validated via GET /api/user/current)
• Sync — 15-min incremental activity feed sync (dashboard/question changes, DB syncs, logins)
• MCP — 14 tools across dashboards, questions, databases, collections, and ad-hoc queries

MCP Tools

Tool	Description
list_dashboards	List all dashboards in Metabase
get_dashboard	Get details of a dashboard including its cards/questions
create_dashboard	Create a new dashboard
update_dashboard	Update a dashboard name or description
list_questions	List all saved questions (cards)
get_question	Get details of a specific saved question
execute_question	Run a saved question and return its results
execute_query	Execute an ad-hoc SQL query against any database connection
list_databases	List all database connections configured in Metabase
get_database_metadata	Get schema metadata for a database (tables and fields)
sync_database_schema	Trigger a schema sync for a database connection
list_collections	List all collections
get_collection_items	List items (dashboards, questions) inside a collection
get_recent_activity	Get recent activity across all Metabase resources

Files

• integrations/metabase/src/index.ts — MetabaseCLI with SETUP / SYNC / GET_TOOLS / CALL_TOOL handlers
• integrations/metabase/src/account-create.ts — API key validation
• integrations/metabase/src/utils.ts — axios client factory
• integrations/metabase/src/schedule.ts — incremental activity sync (state-tracked via lastSyncTime)
• integrations/metabase/src/mcp/index.ts — 14 MCP tools with Zod validation
• integrations/metabase/scripts/register.ts — DB registration script (DATABASE_URL required)
• apps/webapp/app/components/icons/metabase.tsx + icon-utils.tsx — Metabase icon

Closes #538