Write the notes in an app, a school day at a time

The notes existed but there was nowhere to write them: a CLI command on a
laptop, a tool call through Claude, or a file in a Docker volume. None of
those is reachable from a phone in a lesson, which is where notes are
actually taken.

So: `/app`, served only when WEB_PASSWORD is set. A login, the day's
notes, and a settings page for the Schulcloud token — the one surface
here meant for a person rather than a program.

The shape follows how the notes are written: one note per school day,
one `##` heading per lesson, prose and lists and tables beneath. That
turns out to be the design decision that matters, twice over.

First, it is what lets WebUntis earn its keep. Opening a day with no
note fills in that day's lessons — numbered, with times, teacher and
room, cancellations dropped and substitutions marked. Retyping the
timetable is exactly the work the second upstream exists to avoid, and
"Stunden ergänzen" tops up a note started before the day ended without
touching what is already written.

Second, it changes how notes are indexed. A day note is indexed per
lesson, not whole: search answers "my own note, Deutsch, 18.09.2026"
rather than "my own note, Friday", and `list_notes subject=Deutsch`
finds a day whose frontmatter names no subject at all. Indexed whole,
every hit would read as a weekday and "what did we do in Deutsch" would
match notes whose other five lessons were something else. `lessonHeading`
and `subjectFromHeading` are a loop — the app writes the heading, the
indexer reads the subject back out — and a test holds them to it.

Notes taken in a lesson cannot be retaken, so the editor is built
around not losing them: autosave, every keystroke mirrored to local
storage, a save when the phone locks, and a fallback to the local copy
when the request never arrives. A save that would overwrite a version
the editor never saw is refused and the choice handed back — the notes
folder is synced and open in more than one place, and a phone must not
silently win over a laptop. `replaceNote` is separate from `writeNote`
for that reason: never-overwrite is right for `add_note` and exactly
wrong for an editor.

WEB_PASSWORD is the first credential here a human types, so it is the
first that can be guessed: scrypt at startup, never stored or compared
in the clear, per-address rate limiting — which is not decoration, since
the scrypt cost is itself a denial-of-service vector without it. The
session is a signed HttpOnly SameSite=Strict cookie whose key is derived
from the password, so changing it logs everyone out and there is no
second secret to keep. It opens /api, because a session is the user, and
never /mcp, because nothing in a browser speaks MCP.

Also here, because the app made them matter: frontmatter now reads the
indented `- item` list form editors write, so an Obsidian vault
round-trips its tags; and a four-digit folder is a filing scheme, not a
subject, so `2026/` does not file a school year under one.

357 tests; 106/107 smoke against the local instance, the one failure
being the H5P service that instance does not run.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/config.ts

@@ -63,6 +63,15 @@ export interface Config {
 	/** How often to re-crawl on a timer. Zero = only on demand. */
 	crawlIntervalMs: number;
 
+	/**
+	 * Password for the web app at `/app` — the notes editor and the settings
+	 * page. Unset = the app is not served at all, by the same rule the untis_*
+	 * tools follow: a login screen no password can open is worse than no page.
+	 *
+	 * A credential, and the only one here a person types: it is hashed at
+	 * startup and the plain value is never compared, stored or logged.
+	 */
+	webPassword: string | undefined;
 	/**
 	 * Where the user's own lesson notes live, as Markdown files. Unset = the
 	 * note tools are not offered, the same rule the untis_* tools follow.
@@ -181,6 +190,26 @@ function untisConfig(): UntisConfig | undefined {
 	return { server, school, user, secret };
 }
 
+/**
+ * The app password, or undefined when the app is switched off.
+ *
+ * A length floor and nothing else: this one is typed by a person on a phone,
+ * so demanding punctuation would buy little and cost the thing that actually
+ * matters, which is that they pick something long. The error states the rule
+ * and never echoes the value.
+ */
+function webPassword(): string | undefined {
+	const value = process.env.WEB_PASSWORD;
+	if (!value) return undefined;
+	if (value.length < 12) {
+		throw new Error(
+			'WEB_PASSWORD must be at least 12 characters — it is the only thing between the internet and the ' +
+				'notes app. A passphrase of three or four words is ideal.',
+		);
+	}
+	return value;
+}
+
 /** Like `int`, but 0 is meaningful (it disables the feature) rather than invalid. */
 function intAllowingZero(name: string, fallback: number): number {
 	const raw = process.env[name]?.trim();
@@ -231,6 +260,7 @@ export function loadConfig(): Config {
 		crawlIntervalMs: intAllowingZero('CRAWL_INTERVAL_MS', 6 * 60 * 60_000),
 		// Absolute for the same reason as the mirror: resolveWithin only returns
 		// an absolute path when the root it is given is one.
+		webPassword: webPassword(),
 		notesDir: process.env.NOTES_DIR?.trim() ? resolve(process.env.NOTES_DIR.trim()) : undefined,
 		notesWritable: !bool('NOTES_READONLY', false),
 		untisHistoryDays: intAllowingZero('UNTIS_HISTORY_DAYS', 180),