deps: update vendor dependencies for S3-compatible storage

Updates AWS SDK and removes Blazer B2 dependency in favor of unified
S3-compatible approach. Includes configuration examples and documentation.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

vendor/github.com/aws/aws-sdk-go/internal/shareddefaults/ecs_container.go

@@ -0,0 +1,12 @@
+package shareddefaults
+
+const (
+	// ECSCredsProviderEnvVar is an environmental variable key used to
+	// determine which path needs to be hit.
+	ECSCredsProviderEnvVar = "AWS_CONTAINER_CREDENTIALS_RELATIVE_URI"
+)
+
+// ECSContainerCredentialsURI is the endpoint to retrieve container
+// credentials. This can be overridden to test to ensure the credential process
+// is behaving correctly.
+var ECSContainerCredentialsURI = "http://169.254.170.2"

vendor/github.com/aws/aws-sdk-go/internal/shareddefaults/shared_config.go

@@ -0,0 +1,40 @@
+package shareddefaults
+
+import (
+	"os"
+	"path/filepath"
+	"runtime"
+)
+
+// SharedCredentialsFilename returns the SDK's default file path
+// for the shared credentials file.
+//
+// Builds the shared config file path based on the OS's platform.
+//
+//   - Linux/Unix: $HOME/.aws/credentials
+//   - Windows: %USERPROFILE%\.aws\credentials
+func SharedCredentialsFilename() string {
+	return filepath.Join(UserHomeDir(), ".aws", "credentials")
+}
+
+// SharedConfigFilename returns the SDK's default file path for
+// the shared config file.
+//
+// Builds the shared config file path based on the OS's platform.
+//
+//   - Linux/Unix: $HOME/.aws/config
+//   - Windows: %USERPROFILE%\.aws\config
+func SharedConfigFilename() string {
+	return filepath.Join(UserHomeDir(), ".aws", "config")
+}
+
+// UserHomeDir returns the home directory for the user the process is
+// running under.
+func UserHomeDir() string {
+	if runtime.GOOS == "windows" { // Windows
+		return os.Getenv("USERPROFILE")
+	}
+
+	// *nix
+	return os.Getenv("HOME")
+}