release: 2.0.0: Panel redesign; new URLs; database from zero

The panel redesign (docs/plans/panel-redesign.md, 27/27). A breaking
release: every panel URL changed and the database starts from a single
baseline - a 1.x /data is not upgraded.

Since the last cut also fixed, all found on the test server:
  - the panel can read the mail queue;
  - port 25 answers with DMARC report ingest on, also next to the
    inbound relay;
  - DMARC reports reach the panel (the delivery service never worked
    since 1.7.0);
  - Postfix start-up warnings about the queue directory.

Cut: CHANGELOG [Unreleased] -> [2.0.0]; image pin 2.0.0 in compose,
README, guide; roadmap, plan and version table.

On the test server, on 252e5d1: go vet ./... ok, go test ./... ok
(22 packages), make e2e ok.

Full detail: CHANGELOG.md (2.0.0).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/development.md

@@ -107,7 +107,7 @@ than the default «meaningful step» rule in [§ Commits and release build](#com
 2. Git tag `vX.Y.Z` and publish the GitHub Release only on explicit request (see
    [§ Release image](#release-image)).
 
-**Planned version cuts** (from pin `1.9.5`; adjust if semver changes mid-track):
+**Planned version cuts** (from pin `2.0.0`; adjust if semver changes mid-track):
 
 | Stage | ID | Cut |
 |---|---|---|
@@ -123,7 +123,7 @@ than the default «meaningful step» rule in [§ Commits and release build](#com
 | 10 | panel-redesign prep (docs only, owner-requested cut) | `1.9.3` (PATCH) |
 | 11 | panel-redesign plan: component kit, stages, reorder (docs only, owner-requested cut) | `1.9.4` (PATCH) |
 | 12 | GHCR release fix: keep per-arch images, sweep orphaned versions (CI only) | `1.9.5` (PATCH) |
-| 13 | panel-redesign | `2.0.0` (planned; MAJOR, no compatibility) |
+| 13 | panel-redesign | `2.0.0` (MAJOR, no compatibility) |
 | 14 | inbound-antispam-panel | `2.1.0` (planned; was `1.10.0`, reordered 2026-10-09) |
 
 Docs-only prep (checklists in plans, no product code) uses the same per-step