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>

docs/superpowers/plans/2026-07-26-structured-json-logging.md

@@ -4,7 +4,7 @@
 
 **Goal:** Emit structured JSON logs on stdout for (1) every HTTP API request and (2) every Garmin wrapper subprocess call, correlated by a per-request id — without touching any existing `log.Printf` call site.
 
-**Architecture:** A new `internal/applog` package wraps `log/slog` with a JSON handler plus context helpers (`WithLogger`/`FromContext`). `internal/api` gains a `requestLoggingMiddleware` that logs one line per HTTP request and stashes a request-id-tagged logger into the request context. `internal/garmin`'s `client.go` reads that same logger back out of context (via the `ctx` every `Client` method already receives) inside `roundTrip`, the single funnel point all six Garmin calls go through, logging one line per subprocess round-trip.
+**Architecture:** A new `internal/applog` package wraps `log/slog` with a JSON handler plus context helpers (`WithLogger`/`FromContext`). `internal/api` gains a `loggingMiddleware` that logs one line per HTTP request and stashes a request-id-tagged logger into the request context. `internal/garmin`'s `client.go` reads that same logger back out of context (via the `ctx` every `Client` method already receives) inside `roundTrip`, the single funnel point all six Garmin calls go through, logging one line per subprocess round-trip.
 
 **Tech Stack:** Go stdlib `log/slog` (no new dependency), `github.com/go-chi/chi/v5/middleware` (already-available subpackage of the existing chi dependency).
 
@@ -20,7 +20,7 @@
 
 **Files:**
 - Create: `backend/internal/applog/applog.go`
-- Create: `backend/internal/applog/applog_test.go`
+- Create: `../../../backend/internal/log/log_test.go`
 
 **Interfaces:**
 - Produces: `func NewLogger(level string, w io.Writer) *slog.Logger`, `func WithLogger(ctx context.Context, logger *slog.Logger) context.Context`, `func FromContext(ctx context.Context) *slog.Logger` (never nil — falls back to `slog.Default()`).
@@ -91,7 +91,7 @@ func TestFromContext_DefaultsWhenNoneSet(t *testing.T) {
 Run: `cd backend && go test ./internal/applog/... -v`
 Expected: FAIL — package `internal/applog` doesn't exist yet (build failure).
 
-- [ ] **Step 3: Create `backend/internal/applog/applog.go`**
+- [ ] **Step 3: Create `../../../backend/internal/log/log.go`**
 
 ```go
 // Package applog provides geniusrun's structured JSON logging: a
@@ -164,19 +164,19 @@ git commit -m "feat(applog): add JSON logger and context helpers"
 ### Task 2: HTTP access log middleware
 
 **Files:**
-- Modify: `backend/internal/config/config.go` (new `LogLevel` field)
-- Modify: `backend/internal/config/config_test.go` (new tests)
+- Modify: `../../../backend/internal/config/envconfig.go` (new `LogLevel` field)
+- Modify: `../../../backend/internal/config/envconfig_test.go` (new tests)
 - Modify: `backend/cmd/geniusrund/main.go` (wire up `slog.SetDefault`)
-- Modify: `backend/internal/api/server.go` (`requestLoggingMiddleware`, registered in `Router()`)
+- Modify: `backend/internal/api/server.go` (`loggingMiddleware`, registered in `Router()`)
 - Modify: `backend/internal/api/api_test.go` (new tests)
 
 **Interfaces:**
 - Consumes: `applog.NewLogger`, `applog.WithLogger`, `applog.FromContext` (Task 1).
-- Produces: `requestLoggingMiddleware` (unexported chi middleware in `internal/api`), `config.Config.LogLevel string`.
+- Produces: `loggingMiddleware` (unexported chi middleware in `internal/api`), `config.Config.LogLevel string`.
 
 - [ ] **Step 1: Write the failing config tests**
 
-Append to `backend/internal/config/config_test.go`:
+Append to `../../../backend/internal/config/envconfig_test.go`:
 
 ```go
 func TestLoad_LogLevelDefaultsToInfo(t *testing.T) {
@@ -276,7 +276,7 @@ func TestRequestLoggingMiddleware_5xxLogsAtWarnLevel(t *testing.T) {
 Run: `cd backend && go test ./internal/config/... ./internal/api/... -run 'TestLoad_LogLevel|TestRequestLoggingMiddleware' -v`
 Expected: FAIL — `LogLevel` field doesn't exist on `Config`; `applog` import unresolved; no log output produced (middleware doesn't exist).
 
-- [ ] **Step 4: Add `LogLevel` to `config.go`**
+- [ ] **Step 4: Add `LogLevel` to `envconfig.go`**
 
 Change:
 
@@ -471,7 +471,7 @@ Expected: `gofmt -l .` empty; everything passes.
 - [ ] **Step 9: Commit**
 
 ```bash
-git add backend/internal/config/config.go backend/internal/config/config_test.go backend/cmd/geniusrund/main.go backend/internal/api/server.go backend/internal/api/api_test.go
+git add backend/internal/config/envconfig.go backend/internal/config/envconfig_test.go backend/cmd/geniusrund/main.go backend/internal/api/server.go backend/internal/api/api_test.go
 git commit -m "feat(api): add structured JSON access log with request-id correlation"
 ```