chore: add totp feature gate (default-on) + data-encoding + qrcode deps

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

daemon/Cargo.toml

@@ -8,6 +8,10 @@ license.workspace = true
 name = "authforged"
 path = "src/main.rs"
 
+[features]
+default = ["totp"]
+totp = ["dep:data-encoding"]
+
 [dependencies]
 authforge-common = { path = "../common" }
 zbus = { workspace = true }
@@ -27,6 +31,7 @@ toml = { workspace = true }
 ctap-hid-fido2 = { workspace = true }
 hex = { workspace = true }
 argon2 = { workspace = true }
+data-encoding = { workspace = true, optional = true }
 
 [dev-dependencies]
 tempfile = { workspace = true }