diff --git a/.env.example b/.env.example
deleted file mode 100644
index 1d0205a..0000000
--- a/.env.example
+++ /dev/null
@@ -1,3 +0,0 @@
-BASIC_AUTH_USER=admin
-BASIC_AUTH_PASSWORD=change-me
-# HEATPUMP_PORT=8080
diff --git a/.gitignore b/.gitignore
deleted file mode 100644
index 4c49bd7..0000000
--- a/.gitignore
+++ /dev/null
@@ -1 +0,0 @@
-.env
diff --git a/README.md b/README.md
index 4124447..55b982c 100644
--- a/README.md
+++ b/README.md
@@ -3,7 +3,8 @@
 A small static web app that visualises when a heat pump compressor is running,
 based on Home Assistant history exports (`binary_sensor.*` on/off states).
 
-- Interactive timeline (pan, zoom, mouse-wheel, quick ranges 6 h / 24 h / 3 d / 7 d)
+- Interactive timeline (pan, zoom, mouse-wheel, quick ranges 6 h / 24 h / 3 d / 7 d;
+  double-click or Esc resets the zoom)
 - Hover an on-phase to see its start, end and duration
 - Statistics for the visible range: number of phases, min / max / mean / median
   duration, total on-time, duty cycle, mean pause between phases
@@ -20,13 +21,18 @@ Put CSV exports into `data/`. Every `*.csv` in there is baked into the image.
 
 - **One file:** it is loaded directly.
 - **Several files:** a dropdown in the header lists them alphabetically. The
-  most recently modified file (or the viewer's last choice) is preselected.
+  viewer's last choice is preselected, otherwise the **last file by name**.
+  Name files by date (`2026-09.csv`, `2026-10.csv`, …) so the newest comes last.
 
 A different CSV can also be opened ad hoc with **Load CSV…**. It is parsed in
 the browser and not uploaded.
 
 The file list comes from nginx's JSON directory listing of `/data/`, so nothing
-has to be registered anywhere. Add or remove files and rebuild the image.
+has to be registered anywhere. To add or remove files, commit and push; CI
+builds a new image. Locally, use `docker compose up -d --build`.
+
+> The data is part of the image. Anyone who can pull the image (or read this
+> repository) can read the CSVs; basic auth only protects the running web app.
 
 ### CSV format
 
@@ -76,11 +82,12 @@ the app without a password.
 ### Local run with Compose
 
 ```sh
-cp .env.example .env   # set BASIC_AUTH_USER / BASIC_AUTH_PASSWORD
 docker compose up -d --build
 ```
 
-Open <http://localhost:8080> (port configurable with `HEATPUMP_PORT`).
+Open <http://localhost:8080> and log in as `dev` / `dev`. These development
+credentials are set in `docker-compose.yml`. The host port can be changed with
+`HEATPUMP_PORT=9000 docker compose up -d`.
 
 ## CI: build and push
 
@@ -102,7 +109,9 @@ Setup:
    - `REGISTRY_TOKEN`: that robot account's secret
 2. A runner with Docker access must be registered for the repo, user or
    instance (`act_runner` with the Docker socket mounted), and it must provide
-   the `ubuntu-latest` label.
+   the `ubuntu-latest` label. The job image needs Node 20 and the Docker CLI,
+   e.g. `docker.gitea.com/runner-images:ubuntu-latest`. The old default
+   `node:16-bullseye` fails on `actions/checkout@v4`.
 
 ## Project layout
 
diff --git a/data/history2.csv b/data/history2.csv
deleted file mode 100644
index 70cb55d..0000000
--- a/data/history2.csv
+++ /dev/null
@@ -1,71 +0,0 @@
-entity_id,state,last_changed
-binary_sensor.heatpump_compressor,on,2026-09-17T03:00:19.068Z
-binary_sensor.heatpump_compressor,off,2026-09-17T03:08:01.062Z
-binary_sensor.heatpump_compressor,on,2026-09-17T11:26:17.041Z
-binary_sensor.heatpump_compressor,off,2026-09-17T11:41:03.220Z
-binary_sensor.heatpump_compressor,on,2026-09-18T03:00:22.102Z
-binary_sensor.heatpump_compressor,off,2026-09-18T03:19:35.943Z
-binary_sensor.heatpump_compressor,on,2026-09-18T10:19:43.304Z
-binary_sensor.heatpump_compressor,off,2026-09-18T10:36:39.042Z
-binary_sensor.heatpump_compressor,on,2026-09-19T01:20:46.148Z
-binary_sensor.heatpump_compressor,off,2026-09-19T01:22:54.097Z
-binary_sensor.heatpump_compressor,on,2026-09-19T02:22:51.267Z
-binary_sensor.heatpump_compressor,off,2026-09-19T02:28:06.281Z
-binary_sensor.heatpump_compressor,on,2026-09-19T03:28:40.219Z
-binary_sensor.heatpump_compressor,off,2026-09-19T03:35:46.221Z
-binary_sensor.heatpump_compressor,on,2026-09-19T04:41:58.300Z
-binary_sensor.heatpump_compressor,off,2026-09-19T04:49:50.417Z
-binary_sensor.heatpump_compressor,on,2026-09-19T05:57:54.487Z
-binary_sensor.heatpump_compressor,off,2026-09-19T06:43:11.390Z
-binary_sensor.heatpump_compressor,on,2026-09-19T09:12:49.606Z
-binary_sensor.heatpump_compressor,off,2026-09-19T09:29:53.590Z
-binary_sensor.heatpump_compressor,on,2026-09-20T03:39:39.610Z
-binary_sensor.heatpump_compressor,off,2026-09-20T03:42:03.650Z
-binary_sensor.heatpump_compressor,on,2026-09-20T04:41:55.897Z
-binary_sensor.heatpump_compressor,off,2026-09-20T04:47:38.833Z
-binary_sensor.heatpump_compressor,on,2026-09-20T05:48:38.700Z
-binary_sensor.heatpump_compressor,off,2026-09-20T05:55:45.486Z
-binary_sensor.heatpump_compressor,on,2026-09-20T06:00:23.429Z
-binary_sensor.heatpump_compressor,off,2026-09-20T06:36:28.105Z
-binary_sensor.heatpump_compressor,on,2026-09-20T09:50:15.244Z
-binary_sensor.heatpump_compressor,off,2026-09-20T10:01:52.926Z
-binary_sensor.heatpump_compressor,on,2026-09-21T03:00:04.587Z
-binary_sensor.heatpump_compressor,off,2026-09-21T03:05:11.361Z
-binary_sensor.heatpump_compressor,unknown,2026-09-21T08:18:28.438Z
-binary_sensor.heatpump_compressor,off,2026-09-21T08:18:30.643Z
-binary_sensor.heatpump_compressor,on,2026-09-22T03:00:05.235Z
-binary_sensor.heatpump_compressor,off,2026-09-22T03:20:51.957Z
-binary_sensor.heatpump_compressor,on,2026-09-22T09:45:24.980Z
-binary_sensor.heatpump_compressor,off,2026-09-22T10:05:30.687Z
-binary_sensor.heatpump_compressor,on,2026-09-23T03:00:08.414Z
-binary_sensor.heatpump_compressor,off,2026-09-23T03:12:46.457Z
-binary_sensor.heatpump_compressor,on,2026-09-23T09:45:29.000Z
-binary_sensor.heatpump_compressor,off,2026-09-23T10:04:03.857Z
-binary_sensor.heatpump_compressor,on,2026-09-24T03:00:09.997Z
-binary_sensor.heatpump_compressor,off,2026-09-24T03:11:26.925Z
-binary_sensor.heatpump_compressor,on,2026-09-24T12:34:34.499Z
-binary_sensor.heatpump_compressor,off,2026-09-24T13:05:30.499Z
-binary_sensor.heatpump_compressor,on,2026-09-25T03:00:07.285Z
-binary_sensor.heatpump_compressor,off,2026-09-25T03:39:07.324Z
-binary_sensor.heatpump_compressor,unknown,2026-09-25T08:35:58.362Z
-binary_sensor.heatpump_compressor,off,2026-09-25T08:36:05.755Z
-binary_sensor.heatpump_compressor,unknown,2026-09-25T08:36:57.698Z
-binary_sensor.heatpump_compressor,off,2026-09-25T08:36:58.846Z
-binary_sensor.heatpump_compressor,unknown,2026-09-25T08:41:12.345Z
-binary_sensor.heatpump_compressor,off,2026-09-25T08:41:15.133Z
-binary_sensor.heatpump_compressor,on,2026-09-25T09:28:41.719Z
-binary_sensor.heatpump_compressor,off,2026-09-25T09:54:51.506Z
-binary_sensor.heatpump_compressor,on,2026-09-26T00:42:45.260Z
-binary_sensor.heatpump_compressor,off,2026-09-26T00:44:28.166Z
-binary_sensor.heatpump_compressor,on,2026-09-26T01:18:30.843Z
-binary_sensor.heatpump_compressor,off,2026-09-26T01:23:43.918Z
-binary_sensor.heatpump_compressor,on,2026-09-26T02:10:50.330Z
-binary_sensor.heatpump_compressor,off,2026-09-26T02:18:56.282Z
-binary_sensor.heatpump_compressor,on,2026-09-26T03:08:29.828Z
-binary_sensor.heatpump_compressor,off,2026-09-26T03:17:03.786Z
-binary_sensor.heatpump_compressor,on,2026-09-26T04:07:50.486Z
-binary_sensor.heatpump_compressor,off,2026-09-26T04:17:22.353Z
-binary_sensor.heatpump_compressor,on,2026-09-26T05:06:08.060Z
-binary_sensor.heatpump_compressor,off,2026-09-26T05:16:05.238Z
-binary_sensor.heatpump_compressor,on,2026-09-26T06:00:08.484Z
-binary_sensor.heatpump_compressor,off,2026-09-26T06:37:50.037Z
diff --git a/html/app.js b/html/app.js
index 8f9a0fa..a5cb653 100644
--- a/html/app.js
+++ b/html/app.js
@@ -348,11 +348,11 @@ async function init() {
   }
   state.datasets = files.map(f => f.name);
 
-  // last selection if still present, otherwise the most recently modified file
+  // last selection if still present, otherwise the last file by name
+  // (mtimes are useless here: git checkouts in CI give all files the same time)
   let saved = null;
   try { saved = localStorage.getItem(DATASET_KEY); } catch { /* storage unavailable */ }
-  const newest = files.reduce((a, b) => Date.parse(b.mtime) > Date.parse(a.mtime) ? b : a);
-  loadDataset(state.datasets.includes(saved) ? saved : newest.name);
+  loadDataset(state.datasets.includes(saved) ? saved : state.datasets[state.datasets.length - 1]);
 }
 
 init();