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  - Unused legacy asset `docs/assets/icon.png` (superseded by the four brand SVGs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/store/migrations/0002_sessions.sql

@@ -1,8 +1,8 @@
--- Panel login sessions (spec 7.6.6, plan B.1). Persisted so a login survives a
--- container restart or redeploy; only the SHA-256 of the session token is
--- stored, never the token itself, so a stolen database file cannot be used to
--- sign in. expires_at implements the sliding idle timeout: it is pushed
--- forward on activity rather than being fixed at creation time.
+-- Panel login sessions. Persisted so a login survives a container restart or
+-- redeploy; only the SHA-256 of the session token is stored, never the token
+-- itself, so a stolen database file cannot be used to sign in. expires_at
+-- implements the sliding idle timeout: it is pushed forward on activity rather
+-- than being fixed at creation time.
 CREATE TABLE sessions (
     token_hash TEXT PRIMARY KEY,
     username   TEXT NOT NULL,