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/milter/milter_test.go

@@ -292,8 +292,7 @@ func TestRateLimitDomainAppliesToAnyIP(t *testing.T) {
 		},
 		counts: map[string]int64{store.RateLimitScopeDomain + "|example.com": 999},
 	}
-	// Domain ceilings apply to every client IP; leftover AllowedIPs on the row
-	// are ignored.
+	// Domain ceilings apply to every client IP.
 	if resp := mailFrom(t, rec, limitIP, "a@example.com", "app1"); resp != milter.RespTempFail {
 		t.Fatalf("domain over limit from any IP = %v, want TempFail", resp)
 	}
@@ -362,7 +361,7 @@ func TestAuthIPRestrictOffAllowsAnyIP(t *testing.T) {
 func TestRateLimitInactiveWithoutCeiling(t *testing.T) {
 	rec := &fakeRecorder{
 		limits: map[string]store.RateLimit{
-			store.RateLimitScopeDomain + "|example.com": {AllowedIPs: []string{limitIP}}, // no max/window
+			store.RateLimitScopeDomain + "|example.com": {}, // no max/window
 		},
 		counts: map[string]int64{store.RateLimitScopeDomain + "|example.com": 999},
 	}