Browse the file manager ("Dateien") as a filesystem

Many teachers never use topics or boards; their material sits in the
course's file area, and the tools answered "0 files" for courses holding
dozens of worksheets — 21 of 26 courses on the live account. Persönliche,
Kurs-, Team- and Geteilte Dateien live in the legacy file store, not in
files-storage, and its service is not in the public ingress. The only way in
is the legacy client: HTML listings, and GET /files/signedurl for a
pre-signed download.

core/legacy-files.ts turns that into one path tree — /my, /courses/<course>,
/teams/<team>, /shared — resolving names that contain "/", ids anywhere in a
path, and wrong or ambiguous names with a message saying what is there. A
listing that does not parse throws; it never reads as an empty folder.

Some of the legacy client's GET routes write (GET /files/share/ mints a
share token), so getFileManagerPage allows only the listing routes, by
pattern. Signed URLs are fetched with no credentials and must be https.

- MCP: fs_list, fs_tree, fs_find and fs_read; get_course lists course files.
- CLI: schulcloud fs ls, tree, find and get, recursive and resumable.
- API: /api/fs/list, tree, find and file.
- Index: the crawl walks the file manager (INDEX_FILE_MANAGER, on by
  default), so search covers the text inside those files and sync mirrors
  them under <course>/Kurs-Dateien.

The local instance gains a fixture for all four areas. It needed a loopback,
so signed URLs open from the host, and a pre-created bucket, since MinIO
does not implement PutBucketCors.

135 tests. Smoke 55/55 live; 57/57 and 55/55 on the local instance.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/context.ts

@@ -1,5 +1,6 @@
 import type { Config } from './config.ts';
 import { SchulcloudClient } from './core/client.ts';
+import { FileManager } from './core/legacy-files.ts';
 import type { LegacyUser, MeResponse } from './core/types.ts';
 import type { Indexer } from './indexer/indexer.ts';
 import type { Store } from './store/store.ts';
@@ -14,6 +15,8 @@ import type { Store } from './store/store.ts';
 export class ServerContext {
 	readonly config: Config;
 	readonly client: SchulcloudClient;
+	/** The "Dateien" file manager; shared across sessions when the process provides one. */
+	readonly files: FileManager;
 	/** Shared across sessions; undefined when running without an index. */
 	readonly store: Store | undefined;
 	readonly indexer: Indexer | undefined;
@@ -30,9 +33,13 @@ export class ServerContext {
 	 */
 	private readonly userNames = new Map<string, Promise<string | undefined>>();
 
-	constructor(config: Config, shared?: { client?: SchulcloudClient; store?: Store; indexer?: Indexer }) {
+	constructor(
+		config: Config,
+		shared?: { client?: SchulcloudClient; files?: FileManager; store?: Store; indexer?: Indexer },
+	) {
 		this.config = config;
 		this.client = shared?.client ?? new SchulcloudClient(config);
+		this.files = shared?.files ?? new FileManager(this.client);
 		this.store = shared?.store;
 		this.indexer = shared?.indexer;
 	}