feat(import): add CSV bulk import for notes

Add client-side CSV parsing and bulk import API endpoint for importing
notes from CSV files. Supports quoted fields, newlines in values, and
escaped quotes.

- New POST /api/decks/{deckId}/notes/import endpoint for bulk creation
- CSV parser with RFC 4180 compliance
- Multi-phase import modal (upload → validate → preview → import)
- Client-side validation with per-row error reporting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 159 insertions, 0 deletions

diff --git a/src/client/utils/csvParser.test.ts b/src/client/utils/csvParser.test.ts
new file mode 100644
index 0000000..616e3e8
--- /dev/null
+++ b/src/client/utils/csvParser.test.ts
@@ -0,0 +1,159 @@
+import { describe, expect, it } from "vitest";
+import { parseCSV } from "./csvParser";
+
+describe("parseCSV", () => {
+	it("parses simple CSV with headers", () => {
+		const csv = `deck,note_type,Front,Back
+English,Basic,hello,world
+English,Basic,goodbye,farewell`;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.headers).toEqual([
+				"deck",
+				"note_type",
+				"Front",
+				"Back",
+			]);
+			expect(result.data.rows).toHaveLength(2);
+			expect(result.data.rows[0]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: "hello",
+				Back: "world",
+			});
+			expect(result.data.rows[1]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: "goodbye",
+				Back: "farewell",
+			});
+		}
+	});
+
+	it("handles quoted fields with commas", () => {
+		const csv = `deck,note_type,Front,Back
+English,Basic,"hello, world","foo, bar"`;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.rows[0]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: "hello, world",
+				Back: "foo, bar",
+			});
+		}
+	});
+
+	it("handles quoted fields with newlines", () => {
+		const csv = `deck,note_type,Front,Back
+English,Basic,"line1
+line2","back"`;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.rows).toHaveLength(1);
+			expect(result.data.rows[0]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: "line1\nline2",
+				Back: "back",
+			});
+		}
+	});
+
+	it("handles escaped quotes", () => {
+		const csv = `deck,note_type,Front,Back
+English,Basic,"say ""hello""",world`;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.rows[0]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: 'say "hello"',
+				Back: "world",
+			});
+		}
+	});
+
+	it("skips empty lines", () => {
+		const csv = `deck,note_type,Front,Back
+English,Basic,hello,world
+
+English,Basic,goodbye,farewell
+`;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.rows).toHaveLength(2);
+		}
+	});
+
+	it("handles CRLF line endings", () => {
+		const csv = "deck,note_type,Front,Back\r\nEnglish,Basic,hello,world\r\n";
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.rows).toHaveLength(1);
+			expect(result.data.rows[0]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: "hello",
+				Back: "world",
+			});
+		}
+	});
+
+	it("returns error for empty file", () => {
+		const result = parseCSV("");
+
+		expect(result.success).toBe(false);
+		if (!result.success) {
+			expect(result.error.message).toBe("CSV file is empty");
+		}
+	});
+
+	it("returns error for inconsistent column count", () => {
+		const csv = `deck,note_type,Front,Back
+English,Basic,hello`;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(false);
+		if (!result.success) {
+			expect(result.error.message).toBe("Row 2: Expected 4 columns, got 3");
+			expect(result.error.line).toBe(2);
+		}
+	});
+
+	it("trims whitespace from values", () => {
+		const csv = `deck,note_type,Front,Back
+English , Basic , hello , world `;
+
+		const result = parseCSV(csv);
+
+		expect(result.success).toBe(true);
+		if (result.success) {
+			expect(result.data.rows[0]).toEqual({
+				deck: "English",
+				note_type: "Basic",
+				Front: "hello",
+				Back: "world",
+			});
+		}
+	});
+});