chore/docs: move to GitHub as the single home; drop archived-spec references

Codeberg is being retired as the project's public site, so every reference now
points at GitHub. That includes the Go module path (codeberg.org/mix/selfpost →
github.com/mixeme/selfpost): leaving an import path on a host that is going
away would break `go get` and `go install`, so this is not only a docs change.
Touches go.mod, test/e2e/go.mod, all imports, Makefile MODULE, the -ldflags
version stamp in build/Dockerfile and docs/development.md, the licence headers
in the SVG/HTML assets, and README (no more primary/mirror pair).

Comments no longer cite the archived specification. "spec 7.6.1", "spec 5.1"
and friends pointed into docs/archive/specification-v1.0.md, which is marked as
not a source of truth; each is now a reference to the live document that owns
the subject — architecture.md (with section), product.md, security.md or the
README. The review only asked for the 7.x refs (code-review.md § 4), but 4/5/6/
8/9 had the same defect, so they went too. Comments only, no behaviour change.

Also closes the remaining review items: architecture.md gained a Code layers
section with the layer diagram (A2), and TestParseDelivery gained the exotic
mail.log cases (§ 3).

Fixes a bug that last test found: the delivery-line pattern matched status=
greedily, taking the *last* occurrence on the line. Postfix appends the remote
server's reply verbatim, so a rejection whose reply quoted "status=sent" was
filed as a delivered message in the send log. It now takes the first status=
after the recipient, which is the real field.

R7 (CONTRIBUTING.md) moved to roadmap 2.x — one developer, no external PR flow,
so the file would have no audience yet. R1 (compose image tag) and the git tag
stay in roadmap § v1.x as the release-commit steps.

gofmt/go vet clean on both modules; go test ./... green except the three known
Windows-only failures (file perms, backslash paths, renaming an open file).
Not exercised on the dev server — no Docker locally.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/milter/milter.go

@@ -1,13 +1,14 @@
 // Package milter implements the SelfPost journal-milter: a lightweight milter
-// (spec 7.3) attached to Postfix's smtpd_milters alongside OpenDKIM. On the
-// receive path it reads the SASL login, From, recipients and Subject of each
-// accepted message and records one send-log row per (queue-id, recipient),
-// giving the panel a structured, filterable history that raw mail.log cannot.
+// (architecture.md § Mail path) attached to Postfix's smtpd_milters alongside
+// OpenDKIM. On the receive path it reads the SASL login, From, recipients and
+// Subject of each accepted message and records one send-log row per (queue-id,
+// recipient), giving the panel a structured, filterable history that raw
+// mail.log cannot.
 //
 // It is monitoring only: it never rejects, and every callback returns Continue
 // or Accept so a failure of this milter can never block the relay. Postfix is
 // configured with default_action=accept for this milter's socket, so even a
-// crash or hang fails open (spec 7.3).
+// crash or hang fails open (architecture.md § Mail path).
 package milter
 
 import (
@@ -21,13 +22,14 @@ import (
 
 	"github.com/emersion/go-milter"
 
-	"codeberg.org/mix/selfpost/internal/store"
+	"github.com/mixeme/selfpost/internal/store"
 )
 
 // Store is the persistence the milter needs on the receive path: recording
-// accepted messages (spec 7.3) and, for level-2 rate limiting (spec 7.4),
-// looking up the configured limits and counting recent messages. *store.Store
-// satisfies it; tests substitute a fake.
+// accepted messages (architecture.md § Mail path) and, for level-2 rate
+// limiting (README § Rate limiting), looking up the configured limits and
+// counting recent messages. *store.Store satisfies it; tests substitute a
+// fake.
 type Store interface {
 	InsertQueued(e store.SendLogEntry) error
 	InsertRejected(e store.SendLogEntry) error
@@ -37,11 +39,11 @@ type Store interface {
 
 // session accumulates the fields of one message as the milter callbacks fire.
 // Milter macros arrive per-stage and do not accumulate, so each value is
-// captured at the stage that carries it (spec 7.3): SASL login
-// and From at MAIL, each recipient at RCPT, Subject in the headers, and the
-// queue-id at end-of-message. go-milter creates one session per connection; a
-// connection may carry several messages, so per-message fields are reset at
-// MailFrom (the start of every transaction).
+// captured at the stage that carries it (architecture.md § Mail path): SASL
+// login and From at MAIL, each recipient at RCPT, Subject in the headers, and
+// the queue-id at end-of-message. go-milter creates one session per
+// connection; a connection may carry several messages, so per-message fields
+// are reset at MailFrom (the start of every transaction).
 type session struct {
 	milter.NoOpMilter
 	rec Store
@@ -74,8 +76,8 @@ func (s *session) Connect(host, family string, port uint16, addr net.IP, m *milt
 // macros). This is also the earliest stage where both the sending domain (from
 // the sender) and the application (the login) are known, so the level-2 rate
 // limit is enforced here: over the limit, the message is refused with a 4xx
-// tempfail before recipients are even offered (spec 7.4). Enforcement is
-// fail-open — see overLimit.
+// tempfail before recipients are even offered (README § Rate limiting).
+// Enforcement is fail-open — see overLimit.
 func (s *session) MailFrom(from string, m *milter.Modifier) (milter.Response, error) {
 	s.releaseReservations() // a previous transaction that ended without EOM/ABORT
 	s.from = cleanAddress(from)
@@ -161,7 +163,8 @@ func macro(m *milter.Modifier, name string) string {
 }
 
 // record writes one send-log row per recipient. Failures are logged, never
-// propagated: journalling must not affect mail acceptance (spec 7.3).
+// propagated: journalling must not affect mail acceptance (architecture.md §
+// Mail path).
 func (s *session) record(queueID string) {
 	domain := domainOf(s.from)
 	rcpts := s.rcpts
@@ -198,8 +201,9 @@ func cleanAddress(a string) string {
 }
 
 // domainOf returns the lower-cased domain of an email address, or "" if there
-// is no domain part. Sender binding guarantees the From domain equals
-// the application's domain, so this is the sending domain (spec 7.3).
+// is no domain part. Sender binding guarantees the From domain equals the
+// application's domain, so this is the sending domain (architecture.md § Mail
+// path).
 func domainOf(addr string) string {
 	if i := strings.LastIndexByte(addr, '@'); i >= 0 {
 		return strings.ToLower(addr[i+1:])

internal/milter/milter_test.go

@@ -9,7 +9,7 @@ import (
 
 	"github.com/emersion/go-milter"
 
-	"codeberg.org/mix/selfpost/internal/store"
+	"github.com/mixeme/selfpost/internal/store"
 )
 
 // fakeRecorder captures inserts and can be made to fail, to prove the milter

internal/milter/ratelimit.go

@@ -4,19 +4,20 @@ import (
 	"log"
 	"time"
 
-	"codeberg.org/mix/selfpost/internal/store"
+	"github.com/mixeme/selfpost/internal/store"
 )
 
 // overLimit reports whether the message currently being received should be
-// refused under a level-2 differentiated limit (spec 7.4). It checks the
-// domain-level and application-level limits in turn; either being exceeded is
-// enough to refuse.
+// refused under a level-2 differentiated limit (README § Rate limiting). It
+// checks the domain-level and application-level limits in turn; either being
+// exceeded is enough to refuse.
 //
 // It is deliberately fail-open: any store error, or the absence of a usable
-// limit, is treated as "not over limit" so a malfunction of the level-2 limiter
-// can never block mail — Postfix's level-1 anvil limit (spec 5) remains the
-// backstop, and it does not depend on this milter at all. Only a clean count at
-// or above a configured ceiling returns true.
+// limit, is treated as "not over limit" so a malfunction of the level-2
+// limiter can never block mail — Postfix's level-1 anvil limit
+// (architecture.md § Mail path) remains the backstop, and it does not depend
+// on this milter at all. Only a clean count at or above a configured ceiling
+// returns true.
 //
 // A message that passes reserves a slot per applicable limit, released once it
 // reaches the send log (or is abandoned) — see inflight for why the stored
@@ -78,10 +79,10 @@ func (s *session) releaseReservations() {
 	s.reserved = nil
 }
 
-// recordRejected writes a send-log row for a message refused by a level-2 limit
-// (spec 7.4, "опционально фиксирует ... для видимости в UI"), so the rejection
-// shows up in the monitoring screen. Only MAIL-stage fields are known; the write
-// is best-effort and never affects the response.
+// recordRejected writes a send-log row for a message refused by a level-2
+// limit (README § Rate limiting — refusals are recorded too), so the rejection
+// shows up in the monitoring screen. Only MAIL-stage fields are known; the
+// write is best-effort and never affects the response.
 func (s *session) recordRejected() {
 	err := s.rec.InsertRejected(store.SendLogEntry{
 		Domain:   domainOf(s.from),