Phase 7: telemetry and usage (daily rollup + week dashboard)

Build on Phases 1–6. Telemetry already arrived on
restrict/<device>/telemetry; this phase stores it in a daily rollup and
shows it.

- store: migration 003 adds telemetry_daily (device, day, app seconds,
  site seconds). InsertTelemetry maintains the affected days in the same
  transaction; RebuildRollups backfills and repairs it. UsageRange and
  TopUsage serve the week grid and top lists. CapAudit enforces the
  size-capped append-only audit log from AGENTS.md §7.
- web: GET /devices/{id}/usage — Monday-to-Sunday totals plus the top 10
  apps and top 10 sites, using CSP-safe native <progress> bars.
- theme.js: light/dark from the OS preference, with a nav toggle, loaded
  as an external script so the strict CSP still holds.
- cmd/control: `rollup` subcommand; rollup rebuild and audit cap at
  start-up and every 15 minutes.
- Version 0.5.0-phase7 (compose, Makefile, docs).

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

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

internal/store/migrations/003_usage_rollup.sql

@@ -0,0 +1,24 @@
+-- Migration 003 — Phase 7. Daily usage rollup (AGENTS.md §7 retention).
+--
+-- telemetry holds the per-day detail: one row per (device, day, app, domain).
+-- This table is the daily rollup the dashboard reads for a week and that is
+-- kept long. Apps and domains are summed into separate columns on purpose: a
+-- report can carry both for the same session, so adding them together would
+-- double-count the time.
+--
+-- The rollup is written whenever a telemetry report lands and can be rebuilt
+-- from telemetry at any time (store.RebuildRollups), so it is derived data,
+-- never a second source of truth.
+
+CREATE TABLE IF NOT EXISTS telemetry_daily (
+    device_id      INTEGER NOT NULL REFERENCES devices(id),
+    day            TEXT    NOT NULL,          -- YYYY-MM-DD, local day
+    app_seconds    INTEGER NOT NULL DEFAULT 0,
+    domain_seconds INTEGER NOT NULL DEFAULT 0,
+    app_count      INTEGER NOT NULL DEFAULT 0,
+    domain_count   INTEGER NOT NULL DEFAULT 0,
+    updated_at     TEXT    NOT NULL DEFAULT (datetime('now')),
+    PRIMARY KEY (device_id, day)
+);
+
+CREATE INDEX IF NOT EXISTS idx_telemetry_daily_day ON telemetry_daily(day);