env: load ~/.config/ollie/env at server startup

EnsureDefaults now loads the env file before setting path defaults.
This ensures OLLIE_TIER_*, OLLIE_ENABLED_BACKENDS, and all other
user-configured vars are available to tool scripts from the start,
rather than only after the first backend.NewWithName() call.

pkg/env/env.go

@@ -4,6 +4,7 @@
 package env
 
 import (
+	"bufio"
 	"fmt"
 	"os"
 	"path/filepath"
@@ -25,10 +26,11 @@ var managed = []string{
 	"SUPERPOWERD_SOCKET_DIR",
 }
 
-// EnsureDefaults sets default values for any OLLIE_* vars not already present
-// in the process environment.
+// EnsureDefaults loads ~/.config/ollie/env and sets default values for any
+// OLLIE_* vars not already present in the process environment.
 func EnsureDefaults() {
 	home, _ := os.UserHomeDir()
+	LoadFile(filepath.Join(home, ".config", "ollie", "env"))
 	xdgRuntime := os.Getenv("XDG_RUNTIME_DIR")
 	if xdgRuntime == "" {
 		xdgRuntime = fmt.Sprintf("/run/user/%d", os.Getuid())
@@ -54,6 +56,37 @@ func EnsureDefaults() {
 // Set sets a variable in the process environment.
 func Set(k, v string) { os.Setenv(k, v) } //nolint:errcheck
 
+// LoadFile reads KEY=VALUE pairs from path and sets any key not already
+// present in the environment. Lines beginning with # and blank lines are
+// ignored. Missing file is silently ignored.
+func LoadFile(path string) {
+	f, err := os.Open(path)
+	if err != nil {
+		return
+	}
+	defer f.Close()
+
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := strings.TrimSpace(sc.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+		k, v, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+		k = strings.TrimSpace(k)
+		if i := strings.Index(v, " #"); i >= 0 {
+			v = v[:i]
+		}
+		v = strings.TrimSpace(v)
+		if k != "" && os.Getenv(k) == "" {
+			os.Setenv(k, v) //nolint:errcheck
+		}
+	}
+}
+
 // Get returns a variable from the process environment.
 func Get(k string) string { return os.Getenv(k) }