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/client.go

@@ -1,5 +1,5 @@
 // Package garmin wraps a direct garminconnect subprocess (see
-// pyscript/wrapper.py) as a narrow Go client interface, so the rest of
+// wrapper/wrapper.py) as a narrow Go client interface, so the rest of
 // geniusrun never deals with the wire protocol directly.
 package garmin
 
@@ -18,10 +18,10 @@ import (
 	"sync"
 	"time"
 
-	"geniusrun/backend/internal/applog"
+	"geniusrun/backend/internal/log"
 )
 
-//go:embed pyscript/wrapper.py
+//go:embed wrapper/wrapper.py
 var wrapperScript string
 
 // maxWrapperLineBytes bounds one JSON-line response from the wrapper
@@ -57,8 +57,8 @@ type Client interface {
 	Close() error
 }
 
-// Config configures how the Garmin wrapper subprocess is spawned.
-type Config struct {
+// ClientConfig configures how the Garmin wrapper subprocess is spawned.
+type ClientConfig struct {
 	// PythonPath is the python3 interpreter to run the embedded wrapper
 	// script with. Empty defaults to "python3" resolved via PATH.
 	PythonPath     string
@@ -121,7 +121,7 @@ func mapAuthStatus(s string) AuthStatus {
 // subprocessClient is the real Client implementation, backed by a wrapper
 // subprocess spoken to over newline-delimited JSON on stdio.
 type subprocessClient struct {
-	cfg Config
+	cfg ClientConfig
 
 	mu         sync.Mutex // serializes calls; the wrapper holds a single shared Garmin client
 	cmd        *exec.Cmd
@@ -366,7 +366,7 @@ var _ Client = (*subprocessClient)(nil)
 
 // NewClient builds a Client. The subprocess is not spawned until the first
 // call that needs it (Authenticate, or any data call once authenticated).
-func NewClient(cfg Config) Client {
+func NewClient(cfg ClientConfig) Client {
 	return &subprocessClient{cfg: cfg}
 }