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/mock.go

@@ -0,0 +1,114 @@
+// MockClient support: a fake Client for tests and frontend/dev
+// work without a live Garmin account or the wrapper subprocess.
+package garmin
+
+import (
+	"context"
+	"time"
+)
+
+// MockClient is a fake Client returning data supplied by the test/caller.
+type MockClient struct {
+	AuthResults []AuthResult // consumed in order by Authenticate/CompleteMFA calls
+	Activities  []Activity
+	Splits      map[int64]ActivitySplits
+	Details     map[int64]ActivityDetails
+	Workouts    map[int64]Workout
+	// WorkoutErrByID, if set for a given workout ID, makes GetWorkoutByID
+	// return that error for that ID specifically -- independent of the
+	// all-calls-fail Err field below -- so a test can simulate one
+	// activity's workout fetch failing while others in the same batch
+	// succeed.
+	WorkoutErrByID map[int64]error
+	// Delay, if set, is slept (ctx-cancellable) at the start of every
+	// GetActivities call -- lets a test give sync.Service's discovering
+	// phase (backfillCore/incrementalSyncCore) real wall-clock duration, so
+	// a concurrent goroutine can observe Progress() mid-flight instead of
+	// the call returning instantly.
+	Delay              time.Duration
+	Err                error // if set, every call returns this error
+	authResultCursor   int
+	ClosedCalled       bool
+	GetActivitiesCalls int
+	AuthenticateCalls  int
+	LastEmail          string
+	LastPassword       string
+}
+
+var _ Client = (*MockClient)(nil)
+
+func (c *MockClient) nextAuthResult() AuthResult {
+	if c.authResultCursor >= len(c.AuthResults) {
+		return AuthResult{Status: AuthSuccess, Message: "Authenticated successfully."}
+	}
+	r := c.AuthResults[c.authResultCursor]
+	c.authResultCursor++
+	return r
+}
+
+func (c *MockClient) Authenticate(ctx context.Context) (AuthResult, error) {
+	c.AuthenticateCalls++
+	if c.Err != nil {
+		return AuthResult{}, c.Err
+	}
+	return c.nextAuthResult(), nil
+}
+
+func (c *MockClient) CompleteMFA(ctx context.Context, code string) (AuthResult, error) {
+	if c.Err != nil {
+		return AuthResult{}, c.Err
+	}
+	return c.nextAuthResult(), nil
+}
+
+func (c *MockClient) GetActivities(ctx context.Context, startDate, endDate string, limit int) ([]Activity, error) {
+	c.GetActivitiesCalls++
+	if c.Delay > 0 {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		case <-time.After(c.Delay):
+		}
+	}
+	if c.Err != nil {
+		return nil, c.Err
+	}
+	if limit > 0 && limit < len(c.Activities) {
+		return c.Activities[:limit], nil
+	}
+	return c.Activities, nil
+}
+
+func (c *MockClient) GetActivitySplits(ctx context.Context, activityID int64) (ActivitySplits, error) {
+	if c.Err != nil {
+		return ActivitySplits{}, c.Err
+	}
+	return c.Splits[activityID], nil
+}
+
+func (c *MockClient) GetActivityDetails(ctx context.Context, activityID int64) (ActivityDetails, error) {
+	if c.Err != nil {
+		return ActivityDetails{}, c.Err
+	}
+	return c.Details[activityID], nil
+}
+
+func (c *MockClient) GetWorkoutByID(ctx context.Context, workoutID int64) (Workout, error) {
+	if c.Err != nil {
+		return Workout{}, c.Err
+	}
+	if err, ok := c.WorkoutErrByID[workoutID]; ok {
+		return Workout{}, err
+	}
+	return c.Workouts[workoutID], nil
+}
+
+func (c *MockClient) UpdateCredentials(email, password string) {
+	c.LastEmail = email
+	c.LastPassword = password
+}
+
+func (c *MockClient) Close() error {
+	c.ClosedCalled = true
+	return nil
+}