opt-in usage notes and a stats dashboard

Release builds ask in setup and Settings whether to send a short note when the app is opened and after each drive: the version, plus the Android version, phone model and cars people tick. Nothing runs in the background. Dev builds always send. The Cloudflare Worker in stats-worker/ stores the notes and serves a private dashboard with GitHub downloads alongside.

stats-worker/schema.sql

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+-- One row per phone per day: the first note that day counts, later ones update it.
+CREATE TABLE IF NOT EXISTS pings (
+  day TEXT NOT NULL,          -- YYYY-MM-DD, UTC
+  uid TEXT NOT NULL,          -- salted hash of the phone's random install ID
+  version TEXT NOT NULL,
+  code INTEGER,
+  build TEXT,
+  android TEXT,               -- these four are from older builds; details now live in phones
+  os TEXT,
+  phone TEXT,
+  car_today INTEGER,
+  PRIMARY KEY (day, uid)
+);
+
+-- Each car a phone saw that day, and how the session ended.
+CREATE TABLE IF NOT EXISTS cars (
+  day TEXT NOT NULL,
+  uid TEXT NOT NULL,
+  name TEXT, car TEXT, year TEXT, make TEXT, model TEXT,
+  protocol TEXT,
+  result TEXT,
+  screen TEXT,                -- usable pixels, e.g. 1280x720
+  dpi INTEGER,
+  PRIMARY KEY (day, uid, name, car, year, protocol, result)
+);
+
+CREATE INDEX IF NOT EXISTS pings_uid ON pings (uid);
+
+-- GitHub's running download count for each release's APK, saved once a day.
+CREATE TABLE IF NOT EXISTS downloads (
+  day TEXT NOT NULL,
+  tag TEXT NOT NULL,
+  count INTEGER NOT NULL,
+  PRIMARY KEY (day, tag)
+);
+
+-- Which releases are pre-releases, so the dashboard can pick out the latest full release.
+CREATE TABLE IF NOT EXISTS releases (
+  tag TEXT PRIMARY KEY,
+  prerelease INTEGER NOT NULL,
+  published TEXT
+);
+
+-- Each phone's latest details. Phones send them only when they change (and once a month), so
+-- a field a note leaves out keeps its last value.
+CREATE TABLE IF NOT EXISTS phones (
+  uid TEXT PRIMARY KEY,
+  android TEXT,
+  os TEXT,
+  phone TEXT,
+  updated TEXT
+);