Read the user's own lesson notes, and the class register behind them

Schulcloud says what was uploaded and WebUntis says what was scheduled.
Neither says what was *taught* — which point the teacher laboured, which
example landed, what "will definitely come up". That lives in two places
this server could not reach: the notes the user takes in the lesson, and
WebUntis' class register.

Notes are a directory of Markdown files (NOTES_DIR), not a table. They
have to be writable from a phone in a classroom, readable when Postgres
is down, and outlive this project, and files are the only shape that is
all three — so the files are the truth and the index is a view of them,
the same split as file_texts and the mirror. list_notes and get_note read
disk, so they answer before the first crawl; search, what_changed and all
three German prompts read them alongside the Schulcloud material.

add_note writes one, and is the only thing in this server that writes
anything. That is not a hole in the read-only invariant but a different
store: it is bounded to NOTES_DIR by the same safeComponent/resolveWithin
pair that stops a hostile Schulcloud filename escaping the mirror, so a
note titled ../../.ssh/authorized_keys becomes a filename. Schulcloud and
WebUntis stay GET-only and allowlisted respectively. NOTES_READONLY
refuses writes outright.

Appending targets the *lesson*, not the title: "halt das auch noch fest"
mid-lesson carries a new title, and deriving the path from it would start
a second note every time, which is the one thing append exists to prevent.

Notes.app has no export — its bodies are compressed protobuf and the
iCloud copy is encrypted — so scripting the app is not the clumsy route
to the notes but the only one. scripts/export-apple-notes.js reads them
through AppleScript into one JSON object per line, and `schulcloud note
import` converts the HTML to Markdown, takes the Notes folder as the
subject and the *creation* date as the lesson's date. Attachments cannot
come across; a note that was a photo of the board imports as a line
saying so, because importing it empty would hide the loss.

The class register needed one API property to become cheap:
getLessonTopic2017 answers per *series*, not per period, so a term is
reconstructed by asking about the latest period of each lesson series and
merging back by id — a few dozen calls for a school year rather than one
per lesson. untis_lesson_topics now takes a subject as well as a period
id, and UNTIS_HISTORY_DAYS of register goes into the index under a kind
of its own, so "what did we actually do before the test" is searchable.

Sharing the snapshot rather than duplicating it caught one thing on the
way: the search tool's live path had to learn notes too, or fresh=true
would have quietly disagreed with the index.

305 tests; 88/89 smoke against the local instance, the one failure being
the H5P service that instance does not run. The live smoke could not be
retaken: that session has lapsed and needs a fresh jwt cookie.

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

src/config.ts

@@ -63,6 +63,25 @@ export interface Config {
 	/** How often to re-crawl on a timer. Zero = only on demand. */
 	crawlIntervalMs: number;
 
+	/**
+	 * 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.
+	 */
+	notesDir: string | undefined;
+	/**
+	 * Whether add_note may write. The notes directory is the only thing in this
+	 * server anything can write to, so turning it off is a real setting and not
+	 * a theoretical one — a deployment that syncs its notes in from elsewhere
+	 * wants the files left alone.
+	 */
+	notesWritable: boolean;
+	/**
+	 * How far back to read the WebUntis class register into the index. Zero =
+	 * not at all. Costs one timetable call per 90 days plus one per lesson
+	 * series, so a school year is a few dozen requests on a background crawl.
+	 */
+	untisHistoryDays: number;
+
 	/**
 	 * WebUntis, where the school keeps the timetable. Unset = the untis_* tools
 	 * are not offered at all, which is the right answer for a school that does
@@ -210,6 +229,11 @@ export function loadConfig(): Config {
 		// so an index without it misses whole courses. One page load per folder.
 		indexFileManager: bool('INDEX_FILE_MANAGER', true),
 		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.
+		notesDir: process.env.NOTES_DIR?.trim() ? resolve(process.env.NOTES_DIR.trim()) : undefined,
+		notesWritable: !bool('NOTES_READONLY', false),
+		untisHistoryDays: intAllowingZero('UNTIS_HISTORY_DAYS', 180),
 		untis: untisConfig(),
 	};
 }