Phase 9: Hub API and Apprise alerts (/capabilities, /ask, /notify)

Build on Phases 1-8. Adds the project side of the frozen Hub contract
(central_ai_llm_master/docs/ask-contract.md) and the alert engine from
AGENTS.md §4 FR-12/FR-13, §8, §11 Phase 9.

- hub: internal/hub implements AskRequest/AskResponse/NotifyRequest and a
  deterministic, read-only Answerer. It answers screen time today/yesterday,
  what is blocked now, and device presence, scoped to one child or all kids.
  Screen time is the foreground-app total per device-day; the domain total is
  used only when a device reports no apps, so a report carrying both is never
  double-counted.
- apprise: internal/apprise is a small Apprise API client (stored key or
  stateless URL mode, optional bearer token, typed notifications).
- alert: internal/alert evaluates device state on an interval and raises one
  Apprise alert per transition: a limit hit (a device becomes blocked) or a
  device offline longer than the threshold. A never-seen device is never
  alerted, and the first observation seeds state without replaying an old
  limit. The alert is recorded before delivery, with its delivery outcome.
- store: migration 005 adds `alerts` (delivery outcome, audited) and
  `alert_state` (per-device dedup). New usage reads from the telemetry detail
  table so the daily answer can be checked independently.
- web: GET /capabilities, POST /ask (read-only) and POST /notify behind the
  shared CONTROL_HUB_TOKEN, separate from the session and admin API tokens.
  /notify accepts the contract's {from,level,message,person} and delivers it
  through Apprise (the future tamper-report path, FR-17).
- cmd/control: start the alert engine (CONTROL_ALERTS_ENABLED,
  CONTROL_ALERT_OFFLINE_AFTER, CONTROL_ALERT_INTERVAL) and add `alerts` and
  `usage` subcommands for read-only inspection.
- deploy/verify-phase9.sh + `make verify-phase9` prove the definition of done;
  version 0.7.0-phase9.

Measured on .13 (2026-10-13):
- GET /capabilities -> internet_use_control topics.
- POST /ask "how long have the kids been on screens today?" -> "The kids have
  had 1h 22m of screen time today." (total_seconds=4925); the independent
  count from the telemetry detail table is also 4925 (app=4925, domain=4800).
- A manual lock raised a delivered limit alert (id 4); an MQTT offline status
  raised a delivered offline alert (id 5); POST /notify delivered (id 6). All
  three report delivered=1 in `alerts`.

Tests: gofmt, go vet ./... and go test ./... pass in golang:1.25-alpine.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

internal/store/migrations/005_alerts.sql

@@ -0,0 +1,33 @@
+-- Migration 005 — Phase 9. Alerts and their dedup state (AGENTS.md §4 FR-13,
+-- §5 screen 6, §11 Phase 9).
+--
+-- `alerts` is the append-only record of every alert the Control Service raised:
+-- a schedule/limit hit, a device offline too long, or an accepted notify. It is
+-- what the Alerts screen reads and what the delivery evidence is checked
+-- against. Nothing is ever edited except the delivery outcome columns.
+--
+-- `alert_state` remembers the last observed condition per device, so an alert
+-- fires once on a transition (unlocked -> locked, reachable -> offline-too-long)
+-- instead of on every poll. It is derived state, safe to delete; the service
+-- re-seeds it without alerting.
+
+CREATE TABLE IF NOT EXISTS alerts (
+    id           INTEGER PRIMARY KEY,
+    device_id    INTEGER REFERENCES devices(id),
+    kind         TEXT    NOT NULL CHECK (kind IN ('limit', 'offline', 'notify')),
+    message      TEXT    NOT NULL,
+    created_at   TEXT    NOT NULL DEFAULT (datetime('now')),
+    delivered    INTEGER NOT NULL DEFAULT 0,
+    delivered_at TEXT,
+    error        TEXT
+);
+
+CREATE INDEX IF NOT EXISTS idx_alerts_created ON alerts(created_at);
+CREATE INDEX IF NOT EXISTS idx_alerts_device ON alerts(device_id);
+
+CREATE TABLE IF NOT EXISTS alert_state (
+    device_id  INTEGER PRIMARY KEY REFERENCES devices(id),
+    locked     INTEGER NOT NULL DEFAULT 0,
+    offline    INTEGER NOT NULL DEFAULT 0,
+    updated_at TEXT    NOT NULL DEFAULT (datetime('now'))
+);