Implement Phase 0+1: project setup, config, database, migrations

- Go module, Makefile, .golangci.yaml, .gitignore, example config
- TOML config loading with validation
- SQLite database with WAL, foreign keys, busy timeout
- Schema migrations: users, webauthn_credentials, notebooks, pages,
  strokes, share_links with indexes and cascading deletes
- 4 tests: open+migrate, idempotent, foreign keys, cascade delete

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/db/migrations.go

@@ -0,0 +1,114 @@
+package db
+
+import (
+	"database/sql"
+	"fmt"
+)
+
+var migrations = []struct {
+	name string
+	sql  string
+}{
+	{
+		name: "001_initial_schema",
+		sql: `
+CREATE TABLE IF NOT EXISTS users (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    username      TEXT NOT NULL UNIQUE,
+    password_hash TEXT NOT NULL,
+    created_at    INTEGER NOT NULL,
+    updated_at    INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS webauthn_credentials (
+    id              INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id         INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    credential_id   BLOB NOT NULL UNIQUE,
+    public_key      BLOB NOT NULL,
+    name            TEXT NOT NULL,
+    sign_count      INTEGER NOT NULL DEFAULT 0,
+    created_at      INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS notebooks (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    user_id       INTEGER NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    remote_id     INTEGER NOT NULL,
+    title         TEXT NOT NULL,
+    page_size     TEXT NOT NULL,
+    synced_at     INTEGER NOT NULL,
+    UNIQUE(user_id, remote_id)
+);
+
+CREATE TABLE IF NOT EXISTS pages (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    notebook_id   INTEGER NOT NULL REFERENCES notebooks(id) ON DELETE CASCADE,
+    remote_id     INTEGER NOT NULL,
+    page_number   INTEGER NOT NULL,
+    UNIQUE(notebook_id, remote_id)
+);
+
+CREATE TABLE IF NOT EXISTS strokes (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    page_id       INTEGER NOT NULL REFERENCES pages(id) ON DELETE CASCADE,
+    pen_size      REAL NOT NULL,
+    color         INTEGER NOT NULL,
+    style         TEXT NOT NULL DEFAULT 'plain',
+    point_data    BLOB NOT NULL,
+    stroke_order  INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS share_links (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    notebook_id   INTEGER NOT NULL REFERENCES notebooks(id) ON DELETE CASCADE,
+    token         TEXT NOT NULL UNIQUE,
+    expires_at    INTEGER,
+    created_at    INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS schema_migrations (
+    name       TEXT PRIMARY KEY,
+    applied_at INTEGER NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_notebooks_user ON notebooks(user_id);
+CREATE INDEX IF NOT EXISTS idx_pages_notebook ON pages(notebook_id);
+CREATE INDEX IF NOT EXISTS idx_strokes_page ON strokes(page_id);
+CREATE INDEX IF NOT EXISTS idx_share_links_token ON share_links(token);
+CREATE INDEX IF NOT EXISTS idx_webauthn_user ON webauthn_credentials(user_id);
+`,
+	},
+}
+
+func Migrate(database *sql.DB) error {
+	// Ensure schema_migrations table exists
+	_, err := database.Exec(`CREATE TABLE IF NOT EXISTS schema_migrations (
+		name TEXT PRIMARY KEY, applied_at INTEGER NOT NULL)`)
+	if err != nil {
+		return fmt.Errorf("create schema_migrations: %w", err)
+	}
+
+	for _, m := range migrations {
+		var count int
+		err := database.QueryRow("SELECT COUNT(*) FROM schema_migrations WHERE name = ?", m.name).Scan(&count)
+		if err != nil {
+			return fmt.Errorf("check migration %s: %w", m.name, err)
+		}
+		if count > 0 {
+			continue
+		}
+
+		if _, err := database.Exec(m.sql); err != nil {
+			return fmt.Errorf("apply migration %s: %w", m.name, err)
+		}
+
+		if _, err := database.Exec(
+			"INSERT INTO schema_migrations (name, applied_at) VALUES (?, strftime('%s','now'))",
+			m.name,
+		); err != nil {
+			return fmt.Errorf("record migration %s: %w", m.name, err)
+		}
+	}
+
+	return nil
+}