panel-redesign: the 2.0 schema from zero - one baseline, no 1.x chain

Stage 1, step 1. BREAKING: a 1.x database is not migrated.

Schema
  - internal/store/migrations/ holds one file, 0001_init.sql, equal to the
    2.0 schema; 0002..0010 are deleted (they stay in history at 1.9.5). No
    admin table created and dropped, no ALTERs.
  - users.email replaces users.dmarc_report_email: the address is the
    user's own. The default DMARC report address is a user's setting
    (dmarc_default_mode hosted/account/custom/none, dmarc_default_address);
    the instance setting that mirrored the global user's field is gone.
  - domains.dmarc_rua_user_id: a domain follows a named user's default, or
    has an address of its own in dmarc_rua ('' = none). ON DELETE SET NULL
    leaves it at "no reports", never at someone else's default.
  - user_inbound_domains, users.all_domains, users.all_inbound_domains: in
    the schema for the inbound delegation of the next step.
  - users.role is 'global' / 'domain' (was 'domain_admin');
    rate_limits.allowed_ips, unused since 1.9.0, is dropped.

Opening a database
  - The baseline sets PRAGMA application_id ("SP20"). store.Open refuses a
    file that has a schema version without it (ErrForeignSchema) and one
    newer than the build. A 1.x file at user_version 10 would otherwise read
    as already migrated. The refused file is left untouched.

Code
  - Store.DomainDMARCRua is the one place a domain's report address is
    resolved; dnscheck.ResolveDMARCRua and Store.GlobalDMARCReportEmail are
    gone. dmarc.AllowedRecipients, the domain page, the dashboard and the
    DNS re-check go through it.
  - The old templates keep working on the new model until their pages are
    restyled: the Settings form's address field is the account e-mail and
    switches the user's default between it and none; a domain's "Same as
    Settings" makes it follow the user who chose it; a new or imported
    domain follows its creator.
  - Domain export/import: a domain that follows a user exports no address.

Tests: the baseline pinned table by table (TestBaselineSchema), refusal of a
1.x and of a newer database, constraints and cascades of the new columns and
table, resolution in every default mode, the deleted-user case, and the three
bridged handlers.

docs/schema-migrations.md is rewritten for the baseline; roadmap 11/27,
schema-squash marked built.

go test ./...   (Windows)
  ok for every package except two that fail the same way before this commit:
  internal/domain  TestWriteLoadPrivateKeyRoundtrip (file mode on NTFS)
  internal/logtail TestFollowTailsAndRotates (rename of an open file)

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

internal/dnscheck/examples.go

@@ -1,7 +1,6 @@
 package dnscheck
 
 import (
-	"database/sql"
 	"net"
 	"strings"
 )
@@ -48,15 +47,6 @@ func SPFExample(hostname string, serverIPs []string) string {
 	return "v=spf1 " + strings.Join(mechanisms, " ") + " -all"
 }
 
-// ResolveDMARCRua picks the rua= mailbox for a sending domain: per-domain
-// override wins, then the administrator profile, then policy-only (empty).
-func ResolveDMARCRua(domainRua sql.NullString, profileEmail string) string {
-	if domainRua.Valid {
-		return domainRua.String
-	}
-	return profileEmail
-}
-
 // EmailDomain returns the lower-case domain part of addr, or "" when invalid.
 func EmailDomain(addr string) string {
 	addr = strings.TrimSpace(addr)

internal/dnscheck/examples_test.go

@@ -2,7 +2,6 @@ package dnscheck
 
 import (
 	"context"
-	"database/sql"
 	"strings"
 	"testing"
 
@@ -41,21 +40,6 @@ func TestDMARCExample(t *testing.T) {
 	}
 }
 
-func TestResolveDMARCRua(t *testing.T) {
-	inherit := sql.NullString{}
-	if got := ResolveDMARCRua(inherit, "a@b.com"); got != "a@b.com" {
-		t.Errorf("inherit profile = %q", got)
-	}
-	none := sql.NullString{Valid: true}
-	if got := ResolveDMARCRua(none, "a@b.com"); got != "" {
-		t.Errorf("explicit none = %q", got)
-	}
-	custom := sql.NullString{Valid: true, String: "x@y.com"}
-	if got := ResolveDMARCRua(custom, "a@b.com"); got != "x@y.com" {
-		t.Errorf("custom = %q", got)
-	}
-}
-
 func TestExternalReportAuth(t *testing.T) {
 	name, value, ok := ExternalReportAuth("shop.com", "reports@hub.com")
 	if !ok || name != "_report._dmarc.hub.com" || value != "v=DMARC1;" {