panel-redesign: security review of 2.0 - sessions belong to a user by id

Stage 3, step 2. Reviewed by Fable (read-only), fixed by Sonnet with a
failing test before each fix, checked by Opus. No Critical or High
finding: route authorization, tenant isolation by id, the /server/
subtree guard, output encoding and the origin check were found sound.

Fixed
  - M1: a session was keyed by user name and had no link to the user. A
    deleted or renamed user's cookie stayed alive (renewed on every hit,
    before the user was looked up) and became a session of whoever was
    later created under that name, with that account's role. The
    baseline now has sessions.user_id REFERENCES users(id) ON DELETE
    CASCADE; the principal is resolved by id and a session is renewed
    only after its user was found. RenameSession is gone.
  - M2: any user's password change deleted every other user's sessions.
    It ends that user's other sessions only.
  - L1: a password set on the user form ends that user's sessions (an
    administrator editing their own account keeps the current one).
  - L2: store, saslpasswd2 and Postfix reload errors were shown verbatim
    on the application form, the inbound upstream / recipients forms and
    the limit recalculation - pages a domain administrator reaches.
    Validation errors (app.ValidationError, inbound.ValidationError,
    store.ErrNotAutoRateLimit) keep their text; anything else is logged
    and shown as "Could not save ... Check the logs and try again."
  - L3: store.ListDMARCReports treated an empty domain list as "all". It
    takes a scope now (AllDomains or a list; an empty list is no rows),
    and the DMARC hub is open to the domain role as the plan says: the
    reports of the assigned domains, without the instance-wide ingest
    box. The menu entry was already shown to them and led to a 404.
  - I1: /static/ answered with a listing of the embedded assets. A path
    that is not a known asset is a 404.

Consequences
  - The global DMARC hub lists reports of domains that were deleted
    since, too.
  - dev/migrate1x (not in the tree) no longer carries sessions over:
    everyone signs in again after the transfer.
  - docs/schema-migrations.md: the sessions row.

Recorded, not changed - for the owner:
  - L4: the report-address select names the followed user and their
    address to every administrator of the domain, by default the global
    administrator's login name. The plan asks for it.
  - L5: a delegated inbound upstream may be any host and port, loopback
    and private ranges included - within the trusted-operator model; to
    be listed among the accepted risks in security.md.
  - L6: Account's profile is saved without the password; becomes a
    requirement once password-reset mails to users.email.
  - Still echoing an error's text: backup and domain import (global
    only), the domain form's validation messages.

Not checked by the review: anything needing the container (e2e, real
Postfix / DNS), CSP behaviour in a live browser.

  go test -count=1 ./internal/web/... ./internal/store/... ./internal/app/...
    ./internal/inbound/... ./internal/dmarc/... ./cmd/panel
      ok  (all eleven packages; dev/migrate1x also ok)

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

internal/store/ratelimit_auto.go

@@ -2,6 +2,7 @@ package store
 
 import (
 	"database/sql"
+	"errors"
 	"fmt"
 	"log"
 	"math"
@@ -27,15 +28,20 @@ func (s *Store) RecalcAllAutoRateLimits(retentionDays, l1Max, l1Window int) (int
 	return updated, nil
 }
 
-// RecalcAutoRateLimit recomputes one auto-mode limit. Returns an error when
-// the row is missing or not in auto mode.
+// ErrNotAutoRateLimit is returned by RecalcAutoRateLimit for a limit that is
+// missing or not in auto mode: there is nothing to recalculate. It is the one
+// refusal of that call that is the administrator's to read.
+var ErrNotAutoRateLimit = errors.New("rate limit not in auto mode")
+
+// RecalcAutoRateLimit recomputes one auto-mode limit. Returns
+// ErrNotAutoRateLimit when the row is missing or not in auto mode.
 func (s *Store) RecalcAutoRateLimit(scope string, refID int64, retentionDays, l1Max, l1Window int) error {
 	rl, ok, err := s.GetRateLimit(scope, refID)
 	if err != nil {
 		return err
 	}
 	if !ok || !rl.IsAuto() {
-		return fmt.Errorf("rate limit not in auto mode")
+		return ErrNotAutoRateLimit
 	}
 	rl.Scope, rl.RefID = scope, refID
 	return s.recalcAutoRateLimit(rl, retentionDays, l1Max, l1Window)