release: 1.9.2: Review pass: port-25 milters, DMARC validation, rate-limit fix

Review pass over `1.4.0`…`1.9.1`: port 25 no longer shares the submission milter chain, DMARC reports are validated before they are stored, and the auto rate limit is correct for a non-default level-1 window. Schema migration `0010` (index only). Upgrading is a tag bump.
Added:
  - SQLite migration `0010_send_log_app_login_index.sql` —
  - DMARC aggregate reports are accepted as **zip** as well as gzip or plain XML
  - e2e: `checkPort25ConfigCombinations` regenerates the Postfix configuration
Changed:
  - README hero line and a **Positioning** block in `docs/product.md` record the
Fixed:
  - The setup account's password is hashed at bcrypt cost `12` like every other
  - Login/setup rate limiter: protecting blocked buckets from eviction is now
  - `postqueue -p` output is bounded to 4 MiB (the timeout alone left the size of
  - [schema-migrations.md](docs/schema-migrations.md): the schema section was
  - postqueue reader is now time-bounded: `postqueue -p` runs under a 5-second
  … (11 more in CHANGELOG)
Changed:
  - [roadmap.md](docs/roadmap.md) now carries everything the 2026-08-19 code
  - Extracted `internal/configsafe` — the empty-value and forbidden-character
  - Build, deploy and migration comments no longer cite the archived
  - Dropped the `parseDomainRateLimitForm` / `parseAppRateLimitForm` pass-through
  - Extracted shared helpers: `internal/atomicfile` (atomic temp-write+rename) and
  … (7 more in CHANGELOG)
Removed:
  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs
  - Plan documents for already-shipped features: `domain-stats-auto-ratelimit`,

Full detail: CHANGELOG.md (1.9.2).

internal/web/view/templates/domain_detail.html

@@ -330,8 +330,11 @@
               <div class="check-col">
                 <p class="check-col-title">Client IP allow-list
                   {{if .AuthIPRestrict}}<span class="st st-ok">active</span>{{else}}<span class="st st-unknown">off</span>{{end}}</p>
-                <p class="muted">When enabled, only these addresses may authenticate
-                and submit mail as this application. When off, any client IP is allowed.</p>
+                <p class="muted">When enabled, only these addresses may submit mail as
+                this application; a login from anywhere else is refused with a 4xx at
+                <code>MAIL FROM</code>. When off, any client IP is allowed. Like the
+                level-2 rate limit this runs in the journal-milter and is fail-open —
+                it is a sending control, not an authentication boundary.</p>
                 <form method="post" action="/applications/{{.ID}}/authips">
                   <label class="check-row">
                     <input type="checkbox" name="auth_ip_restrict" value="1"