1.1.0-alpha1: operator-experience polish bundle

First content release on the 1.0.0-stable contract. Three operator-
pain features identified by 1.0.0 production soak, bundled into
one minor release.

- Outlier filtering at ingest (off by default; configurable
  per-metric thresholds; dropped beacons logged at info severity).
- Per-metric and adaptive sampling (sampling_overrides per-metric
  rates; adaptive bumping when measured throughput falls below
  configured floor).
- Deploy-event annotations (new cwv_events table + admin UI at
  /admin/reports/cwv/events for recording deploys, config saves,
  infrastructure changes; time-series overlay rendering ships as
  a 1.1.x patch).

Four new config keys, one new table, four new update hooks
(10030-10033). Settings form expands with three new details
fieldsets. BeaconController gets two new constructor parameters
(KeyValueExpirableFactoryInterface, LoggerInterface) for the
adaptive-throughput counter and outlier-drop logging.

The 1.0.0 contract surfaces (interfaces, beacon payload envelope,
schemas, AsyncContextStore, CwvPanelWeight) are unchanged.
Existing operators see no behaviour change unless they enable
the new opt-in features.

See ROADMAP.md for the 1.1.0 entry; SECURITY.md and PERFORMANCE.md
unchanged from 1.0.0; docs/collector-contract.md unchanged.

Field test handoff: enable outlier filtering on production with
the default thresholds, generate beacons across a few pageviews,
verify watchdog log entries for any dropped outliers; enable
per-metric INP sampling override at 1.0 if INP capture rate has
been low; record a test deploy event via the new admin UI.