refactor: merge internal/sync into internal/garmin, regroup api files and routes

Garmin auth/sync routes move under /api/garmin/*; sync.Service becomes
garmin.Sync with garmin.SyncConfig/ClientConfig; applog becomes
internal/log; the test mock moves into the garmin package as MockClient
(breaking the test-only import cycle the merge created); stale test
URLs and type names updated to match.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/internal/garmin/wrapper/pyproject.toml

@@ -0,0 +1,18 @@
+[project]
+name = "geniusrun-garmin-wrapper"
+version = "0.1.0"
+description = "Subprocess wrapper around garminconnect for geniusrund's internal/garmin package"
+requires-python = ">=3.11"
+dependencies = [
+    "garminconnect",
+]
+
+[project.optional-dependencies]
+dev = ["pytest"]
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[tool.hatch.build.targets.wheel]
+packages = ["."]