feat: Implement Session Token System with /api/v1 base path

- Add migration 000004 for sessions table and performance indexes
- Create session.sql queries for CRUD operations
- Generate session repository code with sqlc
- Create token auth middleware for Echo framework
- Create token handler with create/delete/cleanup endpoints
- Add /api/v1 router with token authentication infrastructure
- Update dbHelper.go to use Up() instead of Migrate(2)
- Update server.go to initialize token handler
- Existing endpoints remain functional (to be deprecated)

New endpoints:
- POST /api/v1/token - Create new session token
- DELETE /api/v1/token - Invalidate token
- POST /api/v1/token/cleanup - Remove expired sessions

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

internal/db/repository/models.go

@@ -6,6 +6,8 @@ package repository
 
 import (
 	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
 )
 
 type Game struct {
@@ -21,6 +23,15 @@ type Game struct {
 	Hash          string     `json:"hash"`
 }
 
+type Session struct {
+	Token      string             `json:"token"`
+	IpAddress  string             `json:"ip_address"`
+	UserAgent  string             `json:"user_agent"`
+	ClientType *string            `json:"client_type"`
+	ExpiresAt  pgtype.Timestamptz `json:"expires_at"`
+	CreatedAt  pgtype.Timestamptz `json:"created_at"`
+}
+
 type Song struct {
 	GameID      int32   `json:"game_id"`
 	SongName    string  `json:"song_name"`

internal/db/repository/session.sql.go

@@ -0,0 +1,120 @@
+// Code generated by sqlc. DO NOT EDIT.
+// versions:
+//   sqlc v1.31.1
+// source: session.sql
+
+package repository
+
+import (
+	"context"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+const createSession = `-- name: CreateSession :one
+INSERT INTO sessions (token, ip_address, user_agent, client_type, expires_at)
+VALUES ($1, $2, $3, $4, $5)
+RETURNING token, ip_address, user_agent, client_type, expires_at, created_at
+`
+
+type CreateSessionParams struct {
+	Token      string             `json:"token"`
+	IpAddress  string             `json:"ip_address"`
+	UserAgent  string             `json:"user_agent"`
+	ClientType *string            `json:"client_type"`
+	ExpiresAt  pgtype.Timestamptz `json:"expires_at"`
+}
+
+func (q *Queries) CreateSession(ctx context.Context, arg CreateSessionParams) (Session, error) {
+	row := q.db.QueryRow(ctx, createSession,
+		arg.Token,
+		arg.IpAddress,
+		arg.UserAgent,
+		arg.ClientType,
+		arg.ExpiresAt,
+	)
+	var i Session
+	err := row.Scan(
+		&i.Token,
+		&i.IpAddress,
+		&i.UserAgent,
+		&i.ClientType,
+		&i.ExpiresAt,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const deleteExpiredSessions = `-- name: DeleteExpiredSessions :exec
+DELETE FROM sessions
+WHERE expires_at < NOW()
+`
+
+func (q *Queries) DeleteExpiredSessions(ctx context.Context) error {
+	_, err := q.db.Exec(ctx, deleteExpiredSessions)
+	return err
+}
+
+const deleteSession = `-- name: DeleteSession :exec
+DELETE FROM sessions
+WHERE token = $1
+`
+
+func (q *Queries) DeleteSession(ctx context.Context, token string) error {
+	_, err := q.db.Exec(ctx, deleteSession, token)
+	return err
+}
+
+const getSession = `-- name: GetSession :one
+SELECT token, ip_address, user_agent, client_type, expires_at, created_at
+FROM sessions
+WHERE token = $1
+LIMIT 1
+`
+
+func (q *Queries) GetSession(ctx context.Context, token string) (Session, error) {
+	row := q.db.QueryRow(ctx, getSession, token)
+	var i Session
+	err := row.Scan(
+		&i.Token,
+		&i.IpAddress,
+		&i.UserAgent,
+		&i.ClientType,
+		&i.ExpiresAt,
+		&i.CreatedAt,
+	)
+	return i, err
+}
+
+const listSessions = `-- name: ListSessions :many
+SELECT token, ip_address, user_agent, client_type, expires_at, created_at
+FROM sessions
+ORDER BY created_at DESC
+`
+
+func (q *Queries) ListSessions(ctx context.Context) ([]Session, error) {
+	rows, err := q.db.Query(ctx, listSessions)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var items []Session
+	for rows.Next() {
+		var i Session
+		if err := rows.Scan(
+			&i.Token,
+			&i.IpAddress,
+			&i.UserAgent,
+			&i.ClientType,
+			&i.ExpiresAt,
+			&i.CreatedAt,
+		); err != nil {
+			return nil, err
+		}
+		items = append(items, i)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}