feat: phase 0 foundation — monorepo scaffold, backend, frontend, CI, docker

Establishes the skeleton every later phase builds on: Go+Gin API with
zap logging, /api/healthz, SQLite+goose runner; Vite+React18+TS strict+
Tailwind v4 frontend with bento-mono theme tokens; openapi.yaml driving
a generated TS client; oxlint with vendored anti-slop rules; GitHub CI;
multi-stage Dockerfile -> 33.6MB distroless image; docker compose up
serves the blank board.


Generated with [Devin](https://devin.ai)

Authored By: TDvorak <[email protected]>
Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/db/db.go

@@ -0,0 +1,33 @@
+// Package db opens the SQLite database and applies goose migrations.
+package db
+
+import (
+	"database/sql"
+	"embed"
+	"fmt"
+
+	"github.com/pressly/goose/v3"
+	_ "modernc.org/sqlite"
+)
+
+//go:embed migrations/*.sql
+var migrations embed.FS
+
+// Open opens (creating if needed) the SQLite file at path and migrates it
+// to the latest schema. WAL + busy_timeout keep reads snappy under writes.
+func Open(path string) (*sql.DB, error) {
+	dsn := fmt.Sprintf("file:%s?_pragma=busy_timeout(5000)&_pragma=journal_mode(WAL)&_pragma=foreign_keys(1)", path)
+	sqlDB, err := sql.Open("sqlite", dsn)
+	if err != nil {
+		return nil, fmt.Errorf("open sqlite: %w", err)
+	}
+
+	goose.SetBaseFS(migrations)
+	if err := goose.SetDialect("sqlite3"); err != nil {
+		return nil, fmt.Errorf("goose dialect: %w", err)
+	}
+	if err := goose.Up(sqlDB, "migrations"); err != nil {
+		return nil, fmt.Errorf("migrate: %w", err)
+	}
+	return sqlDB, nil
+}

apps/backend/internal/db/migrations/0001_init.sql

@@ -0,0 +1,9 @@
+-- +goose Up
+-- Key/value store for user prefs (theme, renderer, ...). Values are JSON.
+CREATE TABLE settings (
+    key   TEXT PRIMARY KEY,
+    value JSON NOT NULL
+);
+
+-- +goose Down
+DROP TABLE settings;