feat: add env file support and parameterize SQL queries

Add .env and .env.local loading with InitEnv() helper that reads
environment variables from config files without overwriting existing
values.

Refactor SQL queries to use parameterized arguments instead of
string formatting for LIMIT/OFFSET clauses, improving query security
and preventing SQL injection vulnerabilities.

Clean up unnecessary rows.Close() calls and simplify error handling
in database query functions.

src/config.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"os"
+	"path/filepath"
 	"time"
 )
 
@@ -23,6 +24,28 @@ func loadConfig() Config {
 	}
 }
 
+func loadEnvFile(envFile string) {
+	if _, err := os.Stat(envFile); err != nil {
+		return
+	}
+
+	data, err := os.ReadFile(envFile)
+	if err != nil {
+		return
+	}
+
+	for _, line := range splitLines(data) {
+		parts := splitKV(line)
+		if len(parts) == 2 {
+			key := parts[0]
+			value := unquote(parts[1])
+			if os.Getenv(key) == "" {
+				os.Setenv(key, value)
+			}
+		}
+	}
+}
+
 func getEnv(key, defaultValue string) string {
 	if v := os.Getenv(key); v != "" {
 		return v
@@ -39,3 +62,53 @@ func parseDuration(key string, defaultVal time.Duration) time.Duration {
 	}
 	return defaultVal
 }
+
+func splitLines(data []byte) []string {
+	lines := make([]string, 0)
+	var line string
+	for _, b := range data {
+		if b == '\n' {
+			lines = append(lines, line)
+			line = ""
+		} else if b != '\r' {
+			line += string(b)
+		}
+	}
+	if line != "" {
+		lines = append(lines, line)
+	}
+	return lines
+}
+
+func splitKV(line string) []string {
+	for i, b := range line {
+		if b == '=' {
+			return []string{line[:i], line[i+1:]}
+		}
+	}
+	return nil
+}
+
+func unquote(s string) string {
+	if len(s) >= 2 && s[0] == '"' && s[len(s)-1] == '"' {
+		return s[1 : len(s)-1]
+	}
+	if len(s) >= 2 && s[0] == '\'' && s[len(s)-1] == '\'' {
+		return s[1 : len(s)-1]
+	}
+	return s
+}
+
+func InitEnv() {
+	possibleFiles := []string{
+		".env",
+		".env.local",
+	}
+	for _, f := range possibleFiles {
+		abs, err := filepath.Abs(f)
+		if err == nil {
+			loadEnvFile(abs)
+			return
+		}
+	}
+}