feat(apply): make the per-env approval gate hermetic (§3 M3 / Track A M1)

The per-env approval policy was applier-supplied — a hand-crafted request
that omitted `project.environments` was ungated, and flipping a gate to
`confirm = false` in the same request un-gated it. Persist the policy
server-side and enforce against `persisted ∪ declared`.

- Migration 0067: `project_environments (project_id, env_name, confirm)`,
  CASCADE on the project. Written declaratively (delete-then-insert) inside
  `upsert_project_tx`, same tx as the project row + node claim.
- `ProjectRepository::get_environments_by_slug` (read side) +
  `ApplyService::effective_env_policy` union the persisted policy with the
  request's declared one (confirm if EITHER says so — monotonic).
- `env_gate_check` now evaluates the effective policy; the three handlers load
  it before the gate. `plan.approvals_required` is the effective gated set, so
  CI sees a persisted gate even when the manifest omits it.
- The union rule closes both bypasses: an omitted policy still trips a
  persisted gate, and an ungating apply must itself pass the gate (the
  declarative replace then takes effect next time) — TOCTOU-safe.

Pinned by env_approval::{persisted_policy_gates_a_request_that_omits_it,
flipping_a_gate_to_false_in_the_same_request_still_gates} +
projects_repo::get_environments_by_slug_returns_persisted_policy. Schema golden
reblessed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/tests/expected_schema.txt

@@ -318,6 +318,11 @@ table: outbox
   claimed_by: text NULL
   created_at: timestamp with time zone NOT NULL default=now()
 
+table: project_environments
+  project_id: uuid NOT NULL
+  env_name: text NOT NULL
+  confirm: boolean NOT NULL
+
 table: projects
   id: uuid NOT NULL default=gen_random_uuid()
   slug: text NOT NULL
@@ -603,6 +608,9 @@ indexes on outbox:
   idx_outbox_due: public.outbox USING btree (next_attempt_at) WHERE (claimed_at IS NULL)
   outbox_pkey: public.outbox USING btree (id)
 
+indexes on project_environments:
+  project_environments_pkey: public.project_environments USING btree (project_id, env_name)
+
 indexes on projects:
   projects_pkey: public.projects USING btree (id)
   projects_slug_key: public.projects USING btree (slug)
@@ -847,6 +855,10 @@ constraints on outbox:
   [FOREIGN KEY] outbox_app_id_fkey: FOREIGN KEY (app_id) REFERENCES apps(id) ON DELETE CASCADE
   [PRIMARY KEY] outbox_pkey: PRIMARY KEY (id)
 
+constraints on project_environments:
+  [FOREIGN KEY] project_environments_project_id_fkey: FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE
+  [PRIMARY KEY] project_environments_pkey: PRIMARY KEY (project_id, env_name)
+
 constraints on projects:
   [FOREIGN KEY] projects_created_by_fkey: FOREIGN KEY (created_by) REFERENCES admin_users(id) ON DELETE SET NULL
   [PRIMARY KEY] projects_pkey: PRIMARY KEY (id)
@@ -992,3 +1004,4 @@ constraints on vars:
   0064: shared topic queue kinds
   0065: group queues
   0066: projects
+  0067: project environments