Sync PHP backend feature parity: IP detection, database backends, API endpoints, and frontend

- IP detection: Cloudflare IPv6, ULA IPv6, proxy header chain, offline GeoIP DB
- Database: add SQLite (pure Go, no CGo) and MSSQL backends
- API: add JSON result sharing endpoint and ID obfuscation
- Frontend: add modern CSS design, design switcher, favicon
- Compatibility: ?cors parameter support, human-friendly distance rounding
- Update Go to 1.21, add modernc.org/sqlite and maxminddb deps

database/mssql/mssql.go

@@ -0,0 +1,81 @@
+package mssql
+
+import (
+	"database/sql"
+	"fmt"
+	"net/url"
+
+	"github.com/librespeed/speedtest-go/database/schema"
+
+	_ "github.com/denisenkom/go-mssqldb"
+	log "github.com/sirupsen/logrus"
+)
+
+type MSSQL struct {
+	db *sql.DB
+}
+
+func Open(hostname, username, password, database, port string) *MSSQL {
+	if port == "" {
+		port = "1433"
+	}
+
+	query := url.Values{}
+	query.Add("database", database)
+
+	connStr := fmt.Sprintf("sqlserver://%s:%s@%s:%s?%s",
+		url.QueryEscape(username),
+		url.QueryEscape(password),
+		hostname,
+		port,
+		query.Encode(),
+	)
+
+	conn, err := sql.Open("sqlserver", connStr)
+	if err != nil {
+		log.Fatalf("Cannot open MSSQL database: %s", err)
+	}
+
+	return &MSSQL{db: conn}
+}
+
+func (p *MSSQL) Insert(data *schema.TelemetryData) error {
+	stmt := `INSERT INTO speedtest_users (ip, ispinfo, extra, ua, lang, dl, ul, ping, jitter, log, uuid) 
+	         VALUES (@p1, @p2, @p3, @p4, @p5, @p6, @p7, @p8, @p9, @p10, @p11);`
+	_, err := p.db.Exec(stmt,
+		data.IPAddress, data.ISPInfo, data.Extra, data.UserAgent, data.Language,
+		data.Download, data.Upload, data.Ping, data.Jitter, data.Log, data.UUID)
+	return err
+}
+
+func (p *MSSQL) FetchByUUID(uuid string) (*schema.TelemetryData, error) {
+	var record schema.TelemetryData
+	row := p.db.QueryRow(`SELECT * FROM speedtest_users WHERE uuid = @p1`, uuid)
+	if row != nil {
+		var id int64
+		if err := row.Scan(&id, &record.Timestamp, &record.IPAddress, &record.ISPInfo, &record.Extra, &record.UserAgent, &record.Language, &record.Download, &record.Upload, &record.Ping, &record.Jitter, &record.Log, &record.UUID); err != nil {
+			return nil, fmt.Errorf("mssql fetch by uuid: %w", err)
+		}
+	}
+	return &record, nil
+}
+
+func (p *MSSQL) FetchLast100() ([]schema.TelemetryData, error) {
+	var records []schema.TelemetryData
+	rows, err := p.db.Query(`SELECT TOP 100 * FROM speedtest_users ORDER BY timestamp DESC;`)
+	if err != nil {
+		return nil, fmt.Errorf("mssql fetch last 100: %w", err)
+	}
+	if rows != nil {
+		defer rows.Close()
+		for rows.Next() {
+			var record schema.TelemetryData
+			var id int64
+			if err := rows.Scan(&id, &record.Timestamp, &record.IPAddress, &record.ISPInfo, &record.Extra, &record.UserAgent, &record.Language, &record.Download, &record.Upload, &record.Ping, &record.Jitter, &record.Log, &record.UUID); err != nil {
+				return nil, fmt.Errorf("mssql scan row: %w", err)
+			}
+			records = append(records, record)
+		}
+	}
+	return records, nil
+}

database/mssql/telemetry_mssql.sql

@@ -0,0 +1,27 @@
+--
+-- MSSQL database schema for speedtest telemetry
+--
+
+CREATE TABLE [dbo].[speedtest_users](
+    [id]        [bigint] IDENTITY(120,1) NOT NULL,
+    [timestamp] [datetime] NOT NULL,
+    [ip]        [nvarchar](max) NOT NULL,
+    [ispinfo]   [nvarchar](max) NULL,
+    [extra]     [nvarchar](max) NULL,
+    [ua]        [nvarchar](max) NOT NULL,
+    [lang]      [nvarchar](max) NOT NULL,
+    [dl]        [nvarchar](max) NULL,
+    [ul]        [nvarchar](max) NULL,
+    [ping]      [nvarchar](max) NULL,
+    [jitter]    [nvarchar](max) NULL,
+    [log]       [nvarchar](max) NULL,
+    [uuid]      [nvarchar](max) NULL,
+ CONSTRAINT [PK_speedtest_users] PRIMARY KEY CLUSTERED
+(
+    [id] ASC
+) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
+) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]
+GO
+
+ALTER TABLE [dbo].[speedtest_users] ADD  CONSTRAINT [DF_speedtest_users_timestamp]  DEFAULT (getdate()) FOR [timestamp]
+GO