release: cut 1.0.0

Pin compose and local trial to ghcr.io/mixeme/selfpost:1.0.0, close the
CHANGELOG cut, retire implementation-plan and v1.x-closure-plan, and point
e2e/CI comments at development.md.

Co-Authored-By: Composer <noreply@cursor.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

test/e2e/main_test.go

@@ -1,13 +1,13 @@
-// Package e2e is the hermetic container e2e gate (plan C.4): it drives the
-// shipped deploy/docker-compose.yml (plus a test-only override) exactly as an
+// Package e2e is the hermetic container e2e gate: it drives the shipped
+// deploy/docker-compose.yml (plus a test-only override) exactly as an
 // administrator and their applications would, so the class of failure unit
 // tests cannot see — broken container wiring — has one place to be caught
 // before an image is published.
 //
-// It is a separate module on purpose (see ../../docs/implementation-plan.md,
-// item C.4): `go test ./...` in the main module never pulls this in, and its
-// test-only dependencies (DKIM verification) never enter the shipped
-// binaries' build graph.
+// It is a separate module on purpose (see ../../docs/development.md):
+// `go test ./...` in the main module never pulls this in, and its test-only
+// dependencies (DKIM verification) never enter the shipped binaries' build
+// graph.
 package e2e
 
 import (