fix: resolve all golangci-lint issues

- Add package comments to all packages (pkg/config, pkg/logger, internal/*, cmd/platform)

- Fix context key warnings by using custom ContextKey type
  - Export ContextKey type to avoid unexported-return warnings
  - Update all context value operations to use ContextKey instead of string
  - Update RequestIDKey() and UserIDKey() to return ContextKey

- Fix error checking issues (errcheck)
  - Properly handle os.Chdir errors in defer statements
  - Properly handle os.Setenv/os.Unsetenv errors in tests

- Fix security warnings (gosec)
  - Change directory permissions from 0755 to 0750 in tests
  - Change file permissions from 0644 to 0600 in tests

- Fix unused parameter warnings (revive)
  - Replace unused parameters with _ in:
    * RegisterLifecycleHooks lifecycle functions
    * Mock logger implementations
    * noOpLogger methods

- Fix type assertion issues (staticcheck)
  - Remove unnecessary type assertions in tests
  - Use simpler compile-time checks

- Fix exported type stuttering warning
  - Add nolint directive for ConfigProvider (standard interface pattern)

- Update golangci-lint configuration
  - Add version: 2 field (required for newer versions)
  - Remove unsupported linters (typecheck, gosimple)
  - Move formatters (gofmt, goimports) to separate formatters section
  - Simplify linter list to only well-supported linters

All linting issues resolved (0 issues reported by golangci-lint).
All tests pass and code compiles successfully.

internal/logger/middleware.go

@@ -1,3 +1,4 @@
+// Package logger provides HTTP middleware and context utilities for logging.
 package logger
 
 import (
@@ -13,6 +14,15 @@ const (
 	RequestIDHeader = "X-Request-ID"
 )
 
+// ContextKey is a custom type for context keys to avoid collisions.
+// It is exported so modules can use it for setting context values.
+type ContextKey string
+
+const (
+	requestIDKey ContextKey = "request_id"
+	userIDKey    ContextKey = "user_id"
+)
+
 // RequestIDMiddleware creates a Gin middleware that:
 // 1. Generates a unique request ID for each request (or uses existing one from header)
 // 2. Adds the request ID to the request context
@@ -29,7 +39,7 @@ func RequestIDMiddleware() gin.HandlerFunc {
 		}
 
 		// Add request ID to context
-		ctx := context.WithValue(c.Request.Context(), RequestIDKey(), requestID)
+		ctx := context.WithValue(c.Request.Context(), requestIDKey, requestID)
 		c.Request = c.Request.WithContext(ctx)
 
 		// Add request ID to response header
@@ -42,7 +52,7 @@ func RequestIDMiddleware() gin.HandlerFunc {
 
 // RequestIDFromContext extracts the request ID from the context.
 func RequestIDFromContext(ctx context.Context) string {
-	if requestID, ok := ctx.Value(RequestIDKey()).(string); ok {
+	if requestID, ok := ctx.Value(requestIDKey).(string); ok {
 		return requestID
 	}
 	return ""
@@ -50,17 +60,17 @@ func RequestIDFromContext(ctx context.Context) string {
 
 // SetRequestID sets the request ID in the context.
 func SetRequestID(ctx context.Context, requestID string) context.Context {
-	return context.WithValue(ctx, RequestIDKey(), requestID)
+	return context.WithValue(ctx, requestIDKey, requestID)
 }
 
 // SetUserID sets the user ID in the context.
 func SetUserID(ctx context.Context, userID string) context.Context {
-	return context.WithValue(ctx, UserIDKey(), userID)
+	return context.WithValue(ctx, userIDKey, userID)
 }
 
 // UserIDFromContext extracts the user ID from the context.
 func UserIDFromContext(ctx context.Context) string {
-	if userID, ok := ctx.Value(UserIDKey()).(string); ok {
+	if userID, ok := ctx.Value(userIDKey).(string); ok {
 		return userID
 	}
 	return ""