feat: add PostgreSQL persistence layer with Neon DB support

internal/db/db.go

@@ -0,0 +1,29 @@
+package db
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+func Open(databaseURL string) (*pgxpool.Pool, error) {
+	if databaseURL == "" {
+		return nil, fmt.Errorf("database URL is required")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+	defer cancel()
+
+	pool, err := pgxpool.New(ctx, databaseURL)
+	if err != nil {
+		return nil, fmt.Errorf("create connection pool: %w", err)
+	}
+
+	if err := pool.Ping(ctx); err != nil {
+		return nil, fmt.Errorf("ping database: %w", err)
+	}
+
+	return pool, nil
+}

internal/db/migrate.go

@@ -0,0 +1,20 @@
+package db
+
+import (
+	"context"
+	_ "embed"
+	"fmt"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+//go:embed migrations/001_init.sql
+var initSQL string
+
+func Migrate(pool *pgxpool.Pool) error {
+	_, err := pool.Exec(context.Background(), initSQL)
+	if err != nil {
+		return fmt.Errorf("run migration: %w", err)
+	}
+	return nil
+}

internal/db/migrations/001_init.sql

@@ -0,0 +1,106 @@
+-- Tutor Platform Initial Schema
+
+CREATE TABLE IF NOT EXISTS interview_sessions (
+    id TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL,
+    target_role TEXT NOT NULL,
+    stack JSONB NOT NULL DEFAULT '[]',
+    interview_timeline TEXT NOT NULL,
+    questions JSONB NOT NULL DEFAULT '[]',
+    answers JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS learner_profiles (
+    user_id TEXT PRIMARY KEY,
+    target_role TEXT NOT NULL,
+    stack JSONB NOT NULL DEFAULT '[]',
+    interview_timeline TEXT NOT NULL,
+    preferences JSONB NOT NULL DEFAULT '{}',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS learner_mastery (
+    user_id TEXT NOT NULL,
+    concept_id TEXT NOT NULL,
+    concept_label TEXT NOT NULL,
+    state TEXT NOT NULL DEFAULT 'unknown',
+    evidence JSONB NOT NULL DEFAULT '[]',
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    PRIMARY KEY (user_id, concept_id)
+);
+
+CREATE TABLE IF NOT EXISTS learner_misconceptions (
+    id TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL,
+    concept JSONB NOT NULL DEFAULT '{}',
+    description TEXT NOT NULL,
+    evidence JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS learner_interventions (
+    id TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL,
+    kind TEXT NOT NULL,
+    reason TEXT NOT NULL,
+    concept JSONB NOT NULL DEFAULT '{}',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS learner_review_schedules (
+    id TEXT PRIMARY KEY,
+    user_id TEXT NOT NULL,
+    concept JSONB NOT NULL DEFAULT '{}',
+    due_at TIMESTAMPTZ NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS ontology_materials (
+    id TEXT PRIMARY KEY,
+    title TEXT NOT NULL,
+    source_type TEXT NOT NULL,
+    body TEXT NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS ontology_concepts (
+    id TEXT PRIMARY KEY,
+    material_id TEXT NOT NULL,
+    concept_id TEXT NOT NULL,
+    concept_label TEXT NOT NULL,
+    summary TEXT NOT NULL,
+    review_state TEXT NOT NULL DEFAULT 'candidate',
+    evidence JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS ontology_edges (
+    id TEXT PRIMARY KEY,
+    from_concept_id TEXT NOT NULL,
+    to_concept_id TEXT NOT NULL,
+    kind TEXT NOT NULL,
+    evidence JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS ontology_gaps (
+    id TEXT PRIMARY KEY,
+    concept_id TEXT NOT NULL,
+    reason TEXT NOT NULL,
+    evidence JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE TABLE IF NOT EXISTS teaching_asset_prompts (
+    id TEXT PRIMARY KEY,
+    concept_id TEXT NOT NULL,
+    asset_type TEXT NOT NULL,
+    prompt TEXT NOT NULL,
+    model_key TEXT NOT NULL,
+    review_state TEXT NOT NULL DEFAULT 'candidate',
+    requires_model_id_verification BOOLEAN NOT NULL DEFAULT TRUE,
+    source_evidence JSONB NOT NULL DEFAULT '[]',
+    created_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);