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/public/events.public.service.ts

@@ -0,0 +1,102 @@
+import {NachklangFeedbackDB} from '../Feedback.db';
+import {EventConfig, EventSummary, Question, Song} from '../feedback.interface';
+
+/**
+ * Returns all events currently eligible to receive feedback:
+ * published, on or after their concert day, and before the deadline.
+ */
+export const getEligibleEvents = async (): Promise<EventSummary[]> => {
+	let conn = await NachklangFeedbackDB.getConnection();
+	try {
+		const query = `
+			SELECT slug, name, subtitle, event_date, feedback_deadline
+			FROM events
+			WHERE is_published = 1 AND event_date <= CURDATE() AND feedback_deadline >= NOW()
+			ORDER BY event_date DESC`;
+		const rows = await conn.query(query);
+		return rows.map((row: any) => ({
+			slug: row.slug,
+			name: row.name,
+			subtitle: row.subtitle,
+			eventDate: row.event_date,
+			feedbackDeadline: row.feedback_deadline
+		}));
+	} finally {
+		await conn.end();
+	}
+};
+
+export type EventLookupResult =
+	| { status: 'OK'; eventId: number; event: EventConfig }
+	| { status: 'NOT_FOUND' }
+	| { status: 'CLOSED' };
+
+/**
+ * Resolves a slug to its full public config: meta, ordered setlist, ordered
+ * active questions. Distinguishes "unknown slug" from "known but outside
+ * its feedback window" so callers can respond 404 vs 410. Also used
+ * internally by the submission flow, which additionally needs `eventId`.
+ */
+export const getEventConfigBySlug = async (slug: string): Promise<EventLookupResult> => {
+	let conn = await NachklangFeedbackDB.getConnection();
+	try {
+		const eventQuery = `
+			SELECT event_id, slug, name, subtitle, event_date, feedback_deadline, intro_text, is_published
+			FROM events WHERE slug = ?`;
+		const eventRows = await conn.query(eventQuery, [slug]);
+		if (eventRows.length === 0) {
+			return {status: 'NOT_FOUND'};
+		}
+		const eventRow = eventRows[0];
+
+		const eligibleQuery = `
+			SELECT 1 FROM events
+			WHERE event_id = ? AND is_published = 1 AND event_date <= CURDATE() AND feedback_deadline >= NOW()`;
+		const eligibleRows = await conn.query(eligibleQuery, [eventRow.event_id]);
+		if (eligibleRows.length === 0) {
+			return {status: 'CLOSED'};
+		}
+
+		const songsQuery = 'SELECT song_id, title, composer, position FROM songs WHERE event_id = ? ORDER BY position ASC';
+		const songRows = await conn.query(songsQuery, [eventRow.event_id]);
+		const songs: Song[] = songRows.map((row: any) => ({
+			songId: row.song_id,
+			title: row.title,
+			composer: row.composer,
+			position: row.position
+		}));
+
+		const questionsQuery = `
+			SELECT eq.event_question_id, eq.position, q.question_id, q.question_type, q.label, q.help_text
+			FROM event_questions eq
+			INNER JOIN questions q ON q.question_id = eq.question_id
+			WHERE eq.event_id = ? AND eq.is_active = 1
+			ORDER BY eq.position ASC`;
+		const questionRows = await conn.query(questionsQuery, [eventRow.event_id]);
+		const questions: Question[] = questionRows.map((row: any) => ({
+			eventQuestionId: row.event_question_id,
+			questionId: row.question_id,
+			type: row.question_type,
+			label: row.label,
+			helpText: row.help_text,
+			position: row.position
+		}));
+
+		return {
+			status: 'OK',
+			eventId: eventRow.event_id,
+			event: {
+				slug: eventRow.slug,
+				name: eventRow.name,
+				subtitle: eventRow.subtitle,
+				eventDate: eventRow.event_date,
+				feedbackDeadline: eventRow.feedback_deadline,
+				introText: eventRow.intro_text,
+				songs,
+				questions
+			}
+		};
+	} finally {
+		await conn.end();
+	}
+};