v1.2.10 — WordPress.org Plugin Check compliance (real fixes)

Addresses the genuine findings from a Plugin Check scan (false positives left documented, per the "real fixes only" scope).

• SettingsPage save handler: added wp_unslash() to the ~22 $_POST inputs that were missing it (values were already sanitised via custom sanitisers / int casts / sanitize_* / esc_url_raw) — clears the MissingUnslash warnings.
• The one ERROR (LogRepository::verify_chain() NotPrepared): extended the existing phpcs:ignore. The integrity-scan query has no user input — table name from $wpdb->prefix, LIMIT an (int) cast — nothing to prepare.
• readme.txt: trimmed three over-300-char upgrade notices + backfilled the missing 1.2.7 / 1.2.8 / 1.2.9 upgrade notices + changelog entries.

Left as documented false positives: ClientInfo/NoScriptFlow (already unslashed + sanitised in helpers), custom-table DB queries, platform-handled checkout nonces, error_log/var_export. PHP lint clean; no behaviour change.