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/logtail/logtail_test.go

@@ -9,7 +9,7 @@ import (
 	"testing"
 	"time"
 
-	"codeberg.org/mix/selfpost/internal/store"
+	"github.com/mixeme/selfpost/internal/store"
 )
 
 func TestParseDelivery(t *testing.T) {
@@ -61,6 +61,59 @@ func TestParseDelivery(t *testing.T) {
 			line:   "host postfix/smtpd[10]: 41E862C00D9E: client=unknown[203.0.113.7]",
 			wantOK: false,
 		},
+		{
+			// The remote server's reply is quoted verbatim at the end of the
+			// line and is entirely attacker-influenced text. A "status=" that
+			// appears in there must not win over the real field, or a bounce
+			// would be filed as a success.
+			name:      "status= quoted in the remote reply does not win",
+			line:      "host postfix/smtp[26]: 9F1A2C00D9E: to=<a@example.net>, relay=mx.example.net[203.0.113.9]:25, dsn=5.1.1, status=bounced (host mx.example.net said: 550 5.1.1 unknown status=sent (in reply to RCPT TO command))",
+			wantOK:    true,
+			queueID:   "9F1A2C00D9E",
+			recipient: "a@example.net",
+			status:    store.StatusBounced,
+		},
+		{
+			// Postfix logs the null sender's own delivery (double bounce) with
+			// an empty recipient. It parses, and the empty recipient simply
+			// matches no send-log row — the panel only ever records mail it
+			// accepted from an authenticated client.
+			name:      "null recipient parses with an empty address",
+			line:      "host postfix/smtp[26]: A1B2C3: to=<>, relay=none, delay=0.1, dsn=2.0.0, status=sent (250 OK)",
+			wantOK:    true,
+			queueID:   "A1B2C3",
+			recipient: "",
+			status:    store.StatusSent,
+		},
+		{
+			// An alias/virtual expansion carries orig_to= as well; the address
+			// the message was actually delivered to is the one in to=.
+			name:      "orig_to is ignored in favour of to",
+			line:      "host postfix/lmtp[26]: 4Xk9tS1abcz: to=<real@example.net>, orig_to=<alias@example.net>, relay=x, dsn=2.0.0, status=sent (ok)",
+			wantOK:    true,
+			queueID:   "4Xk9tS1abcz",
+			recipient: "real@example.net",
+			status:    store.StatusSent,
+		},
+		{
+			// Postfix's own delivery agents write these two, but neither is a
+			// final result we model: "deliverable" comes from address
+			// verification probes, and anything unrecognised is dropped rather
+			// than guessed at, leaving the row in its previous state.
+			name:   "unknown status word is not a delivery result",
+			line:   "host postfix/smtp[26]: BEEF01: to=<a@example.net>, relay=x, status=deliverable (ok)",
+			wantOK: false,
+		},
+		{
+			name:   "status matching is case-sensitive, as Postfix writes it",
+			line:   "host postfix/smtp[26]: BEEF02: to=<a@example.net>, relay=x, dsn=4.0.0, status=Deferred (connect timed out)",
+			wantOK: false,
+		},
+		{
+			name:   "cleanup message-id line ignored",
+			line:   "host postfix/cleanup[12]: BEEF03: message-id=<x@example.com>",
+			wantOK: false,
+		},
 	}
 	for _, c := range cases {
 		t.Run(c.name, func(t *testing.T) {