1.1.0-beta1: API freeze for the 1.1.x track

Cut after alpha2 came back from a clean re-test on portal-dev with
both alpha1 findings verified fixed and zero regressions.

Same code as 1.1.0-alpha2 (commit 1322537) plus a ROADMAP docs
bump. The version bump signals API freeze for the 1.1.x track and
asks operators to soak the module on production-shape installs
ahead of rc1.

What 1.1 ships: per-user private-cache mode for authenticated
Drupal users. Responses whose Drupal cache contexts indicate
per-user variation get X-LiteSpeed-Cache-Control: private,max-age=N
automatically; operators do not hand-tag routes or fragments.

Field-test history through alpha cycle:
- Cache-poisoning canary clean across 18 trials.
- Anonymous response back-compat byte-identical to 1.0.0-rc1.
- Two bugs found and fixed in alpha2: admin-route over-emission,
  drush watchdog:show placeholder rendering.
- Status report row dynamic against the .htaccess directive state.
- Update hook lscache_update_8101 idempotent across repeats.

Stability commitment: response-header shape, private_cache.* config
schema, administer lscache permission, and TagHeaderBuilder service
are stable from this release. Path to 1.1.0 stable is bug-fix only.