feat: public_port for managed databases — opt-in 0.0.0.0 bind

Managed databases have always published their port on 127.0.0.1 only.
public_port opts into binding on all interfaces so the database is
reachable off-host. Toggling via PUT recreates the container — the
named data volume survives.

- create accepts public_port; PUT /databases/{id} toggles it
- external rows reject the flag (no container exists)
- CLI: databases create --public, databases update --public/--public=false
- MCP: databases_update tool; UI: create checkbox + per-row toggle

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/database/sqlcdb/querier.go

@@ -77,6 +77,7 @@ type Querier interface {
 	SetDatabaseBackupScheduleByIDAndUser(ctx context.Context, arg SetDatabaseBackupScheduleByIDAndUserParams) error
 	SetDatabaseBackupStatusByID(ctx context.Context, arg SetDatabaseBackupStatusByIDParams) error
 	SetDatabaseNextBackupAt(ctx context.Context, arg SetDatabaseNextBackupAtParams) error
+	SetDatabaseServicePublicPortByIDAndUser(ctx context.Context, arg SetDatabaseServicePublicPortByIDAndUserParams) error
 	SetDatabaseServiceStatusAndConnectionByID(ctx context.Context, arg SetDatabaseServiceStatusAndConnectionByIDParams) error
 	SetDatabaseServiceStatusByID(ctx context.Context, arg SetDatabaseServiceStatusByIDParams) error
 	SetDatabaseServiceStatusByIDAndUser(ctx context.Context, arg SetDatabaseServiceStatusByIDAndUserParams) error