Add "Data Warehouse" tab to Organisation Settings — Connect flow

[gagantrivedi]

Summary

New tab under Organisation Settings that walks the user through connecting a Snowflake warehouse for analytics data delivery. This issue covers the first-time connect flow (empty state → configure → run SQL → test). The connected-state management (status card, disconnect, re-test) is tracked separately in FE-B.

Depends on: #7276 (POST create), #7277 (test), #7279 (GET list)

Flow

Three-step wizard. On page load, call GET /organisations/{id}/integrations/warehouse-connections/ — if the list is non-empty, skip the wizard and render FE-B (connected state). Otherwise enter Step 1.

Step 1 — Configure

• Warehouse type selector: Snowflake (active); BigQuery, Databricks, Redshift shown as greyed-out "coming soon" cards
• Form fields (all pre-filled with defaults; only Account identifier is truly required user input):
  • Account identifier (required, placeholder xy12345.us-east-1)
  • Warehouse (default COMPUTE_WH)
  • Database (default FLAGSMITH)
  • Schema (default ANALYTICS)
  • Role (default FLAGSMITH_LOADER)
  • User (default FLAGSMITH_SERVICE)
• Continue → fires POST /warehouse-connections/. On 201, advance to Step 2. On 409 (already exists), redirect to FE-B. On validation error, surface inline.

Step 2 — Run SQL

• Read-only code block showing the setup_script returned from Step 1, with a Copy button
• Short explainer: "Run this in your Snowflake account (as a user with ACCOUNTADMIN or SECURITYADMIN + SYSADMIN) to grant Flagsmith permission to deliver data."
• Link to Snowflake docs on running scripts
• I've run this, continue → button advances to Step 3
• Back button returns to Step 1 (re-hits POST is not needed; the script is also available via GET if they reopen the page)

Step 3 — Test

• Prominent Test connection button → fires POST /warehouse-connections/{id}/test/
• Loading state while test runs (<5s)
• Success: green checkmark, short message, automatically transitions to the connected view (FE-B scope)
• Failure: red alert with the raw error string from the response, plus two actions:
  • Try again — re-fires the test
  • Back to Step 2 — in case they need to re-run the SQL

States the UI must handle

• No connection configured → Step 1
• Connection exists but not tested → jump straight to Step 3 (the user closed the browser mid-flow; GET returns status: pending_customer_setup)
• Connection exists and tested → render FE-B (out of scope here)

Behaviour on refresh mid-flow

setup_script is persisted server-side and returned by GET, so closing the browser and returning to the tab lands the user in whichever step matches the current status — no data loss.