feat(environments): env CRUD, workspace switcher, CLI + MCP parity (#68)

Environment lanes existed as seeded rows (production/preview/development)
with a per-service environment label, but there was no way to list,
create, or delete them. Adds the management surface and the switcher:

- GET /projects/:id/environments with live service counts (sqlc)
- POST /projects/:id/environments — lowercase dns-label names, 1-50
  chars, unique per project (409 on dupe)
- DELETE /environments/:id — refuses while it holds services (409)
- Workspace service list gains env filter chips with counts plus an
  inline "+ env" creator
- CLI: containr environments list|create|delete (--yes on delete);
  MCP: containr_environments_list/create/delete (delete needs confirm)
- OpenAPI: new Environments tag + ProjectEnvironment schema

Live-verified: list counts, name validation, dupe 409, empty delete,
non-empty 409, CLI list.

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

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

app/frontend/src/lib/api-client.ts

@@ -1321,6 +1321,34 @@ export async function listServicesByProject(projectId: string): Promise<ServiceE
   return normalizeServiceArray(rows);
 }
 
+export interface ProjectEnvironment {
+  id: string;
+  name: string;
+  project_id: string;
+  service_count: number;
+  created_at: string;
+  updated_at: string;
+}
+
+export async function listProjectEnvironments(projectId: string): Promise<ProjectEnvironment[]> {
+  const payload = await requestJson<{ environments?: ProjectEnvironment[] }>(
+    `/projects/${projectId}/environments`,
+  );
+  return payload.environments ?? [];
+}
+
+export async function createProjectEnvironment(projectId: string, name: string): Promise<ProjectEnvironment> {
+  const payload = await requestJson<{ environment: ProjectEnvironment }>(
+    `/projects/${projectId}/environments`,
+    { method: 'POST', body: JSON.stringify({ name }) },
+  );
+  return payload.environment;
+}
+
+export async function deleteProjectEnvironment(environmentId: string): Promise<void> {
+  await requestJson(`/environments/${encodeURIComponent(environmentId)}`, { method: 'DELETE' });
+}
+
 export async function getServiceById(serviceId: string): Promise<ServiceEntity> {
   const payload = await requestJson<RawService | { service?: RawService }>(`/services/${serviceId}`);
   const row = (payload as { service?: RawService }).service ?? (payload as RawService);