Add ReadOnlyIntent connection option to Lite

[erikdarlingdata]

Summary

• Adds ReadOnlyIntent bool property to Lite's ServerConnection model (persisted to servers.json, defaults to false)
• Sets ApplicationIntent=ReadOnly on the connection string when enabled
• Adds checkbox in Add/Edit Server dialog: "Read-only intent (for AG listeners and readable replicas)"
• Test Connection button also respects the setting

Why

Required for users connecting Lite via:

• AG listeners — routes to readable secondary
• Azure SQL failover group endpoints — same listener-based routing
• Business Critical / Managed Instance built-in read replicas (only reachable via intent flag)

Dashboard excluded since it requires a writable PerformanceMonitor database.

Test plan

• Add a server without the checkbox — verify connection string has no ApplicationIntent change
• Add a server with the checkbox — verify ApplicationIntent=ReadOnly in connection string
• Edit an existing server, toggle the checkbox, save — verify persistence
• Test Connection works with the checkbox enabled against a readable replica

🤖 Generated with Claude Code