Add Feedback domain module: public submission flow, admin CRUD, reporting

New /feedback API domain backed by its own FEEDBACK_DB, mirroring the
Calendar domain's router -> service -> DB pool layering:

- Public endpoints (no auth): eligible-events listing, event config,
  submission with honeypot + rate limiting (in-memory + DB backstop).
- Admin endpoints (session-header auth, reusing Calendar's users/sessions
  via a swappable feedback.auth.ts boundary): events/songs/questions CRUD,
  bulk reorder/assignment, aggregated reporting, CSV export.
- Schema in sql/feedback/001_init.sql (8 tables), applied and verified
  against the real FEEDBACK_DB.
- 64 Jest tests covering validation, auth, rate limiting, CSV escaping,
  and report aggregation (pure functions, no DB needed).

Includes fixes from a security review: path traversal defense doesn't
apply here (that's the frontend proxy, separate repo), but the
rate-limiter cluster does - recordSubmission now counts every processed
request (not just successful ones), the in-memory Map evicts empty
entries instead of growing unbounded, FEEDBACK_IP_SALT is required at
boot instead of silently degrading to unsalted hashing, and submission
answer/rating arrays are capped and de-duplicated to bound insert
amplification.

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

src/models/feedback/admin/questions.admin.service.ts

@@ -0,0 +1,98 @@
+import {NachklangFeedbackDB} from '../Feedback.db';
+import {QuestionType} from '../feedback.interface';
+import {AdminQuestion} from './admin.interface';
+
+const mapRow = (row: any): AdminQuestion => ({
+	questionId: row.question_id,
+	label: row.label,
+	helpText: row.help_text,
+	questionType: row.question_type,
+	isArchived: !!row.is_archived
+});
+
+export const listQuestions = async (includeArchived: boolean): Promise<AdminQuestion[]> => {
+	let conn = await NachklangFeedbackDB.getConnection();
+	try {
+		const query = includeArchived
+			? 'SELECT * FROM questions ORDER BY created_at DESC'
+			: 'SELECT * FROM questions WHERE is_archived = 0 ORDER BY created_at DESC';
+		const rows = await conn.query(query);
+		return rows.map(mapRow);
+	} finally {
+		await conn.end();
+	}
+};
+
+export const createQuestion = async (label: string, helpText: string | null, questionType: QuestionType): Promise<number> => {
+	let conn = await NachklangFeedbackDB.getConnection();
+	try {
+		await conn.beginTransaction();
+		const res = await conn.query(
+			'INSERT INTO questions (label, help_text, question_type) VALUES (?,?,?) RETURNING question_id',
+			[label, helpText, questionType]
+		);
+		await conn.commit();
+		return res[0].question_id;
+	} catch (err) {
+		await conn.rollback();
+		throw err;
+	} finally {
+		await conn.end();
+	}
+};
+
+/**
+ * Edits label/help text only. question_type is immutable after creation -
+ * changing it would invalidate existing answers' question_type_snapshot
+ * semantics. The admin UI offers "archive and create new" instead.
+ */
+export const updateQuestion = async (questionId: number, label: string, helpText: string | null): Promise<boolean> => {
+	let conn = await NachklangFeedbackDB.getConnection();
+	try {
+		await conn.beginTransaction();
+		const res = await conn.query('UPDATE questions SET label = ?, help_text = ? WHERE question_id = ?', [label, helpText, questionId]);
+		await conn.commit();
+		return res.affectedRows > 0;
+	} catch (err) {
+		await conn.rollback();
+		throw err;
+	} finally {
+		await conn.end();
+	}
+};
+
+export type RemoveQuestionResult = 'ARCHIVED' | 'DELETED' | 'NOT_FOUND';
+
+/**
+ * Archives (soft delete) a question. Hard-deletes it instead if it has
+ * never been assigned to any event, so an admin's typo doesn't have to
+ * live forever in the library.
+ */
+export const removeQuestion = async (questionId: number): Promise<RemoveQuestionResult> => {
+	let conn = await NachklangFeedbackDB.getConnection();
+	try {
+		await conn.beginTransaction();
+
+		const existsRows = await conn.query('SELECT 1 FROM questions WHERE question_id = ?', [questionId]);
+		if (existsRows.length === 0) {
+			await conn.rollback();
+			return 'NOT_FOUND';
+		}
+
+		const usageRows = await conn.query('SELECT 1 FROM event_questions WHERE question_id = ? LIMIT 1', [questionId]);
+		if (usageRows.length === 0) {
+			await conn.query('DELETE FROM questions WHERE question_id = ?', [questionId]);
+			await conn.commit();
+			return 'DELETED';
+		}
+
+		await conn.query('UPDATE questions SET is_archived = 1 WHERE question_id = ?', [questionId]);
+		await conn.commit();
+		return 'ARCHIVED';
+	} catch (err) {
+		await conn.rollback();
+		throw err;
+	} finally {
+		await conn.end();
+	}
+};