feat: environment model + deployment tracking (phase 3a)

- Environment/Deployment XORM models + migration 010
- Full CRUD API: GET/POST/PATCH/DELETE /environments + /deployments
- Deployment status update endpoint, publishes deployment.* NATS events
- EnvironmentsPage with deploy cards, history accordion, deploy modal
- Sidebar Environments nav item between Pipelines and Settings
- Repo page deployment status badges (env name + SHA pill per
  environment)
- Environment/Deployment types in types/api.ts + environments.ts query
  hooks

internal/models/migrations/010_environments.go

@@ -0,0 +1,13 @@
+package migrations
+
+import (
+	"github.com/forgeo/forgebucket/internal/models"
+	"xorm.io/xorm"
+)
+
+func Run010(engine *xorm.Engine) error {
+	return engine.Sync2(
+		&models.Environment{},
+		&models.Deployment{},
+	)
+}