feat: Implement single sync job management and progress tracking

specs/004-home-sstent-projects/plan.md

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+# Implementation Plan: Simplify Sync Job Management with Progress Tracking
+
+**Branch**: `004-home-sstent-projects` | **Date**: Saturday, October 11, 2025 | **Spec**: /home/sstent/Projects/FitTrack_GarminSync/specs/004-home-sstent-projects/spec.md
+**Input**: Feature specification from `/specs/004-home-sstent-projects/spec.md`
+
+**Note**: This template is filled in by the `/speckit.plan` command. See `.specify/templates/commands/plan.md` for the execution workflow.
+
+## Summary
+
+The feature aims to simplify sync job management for a single-user system by allowing only one sync job at a time and providing progress tracking via a polling API. This involves reintroducing a simplified `SyncJob` model and a `CurrentSyncJobManager` to manage its state, modifying existing sync services to update this state, and creating a new API endpoint (`GET /garmin/sync/status`) for users to monitor progress.
+
+## Technical Context
+
+**Language/Version**: Python 3.13
+**Primary Dependencies**: FastAPI, Pydantic, `garth`, `garminconnect`, `httpx`
+**Storage**: In-memory for `CurrentSyncJobManager`
+**Testing**: Pytest
+**Target Platform**: Linux server
+**Project Type**: Web application (backend)
+**Performance Goals**:
+-   Users can successfully initiate any sync operation and receive an initial confirmation within 2 seconds.
+-   The `GET /garmin/sync/status` API endpoint responds with the current sync status within 500ms, even under moderate load (e.g., 10 requests per second).
+-   Sync progress updates are reflected in the `GET /garmin/sync/status` API with a granularity that provides meaningful feedback to the user (e.g., progress updates at least every 10% completion or every 30 seconds for long syncs).
+**Constraints**: Single-user system, only one sync job active at a time.
+**Scale/Scope**: Single user, managing personal Garmin data synchronization.
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+All gates pass. No violations.
+
+## Project Structure
+
+### Documentation (this feature)
+
+```
+specs/004-home-sstent-projects/
+├── plan.md              # This file (/speckit.plan command output)
+├── research.md          # Phase 0 output (/speckit.plan command)
+├── data-model.md        # Phase 1 output (/speckit.plan command)
+├── quickstart.md        # Phase 1 output (/speckit.plan command)
+├── contracts/           # Phase 1 output (/speckit.plan command)
+└── tasks.md             # Phase 2 output (/speckit.tasks command - NOT created by /speckit.plan)
+```
+
+### Source Code (repository root)
+
+```
+backend/
+├── src/
+│   ├── models/             # For SyncJob model
+│   ├── services/           # For CurrentSyncJobManager and sync logic
+│   └── api/                # For garmin_sync API endpoints
+└── tests/
+    ├── unit/
+    ├── integration/
+    └── api/
+```
+
+**Structure Decision**: The existing "Option 2: Web application" structure is appropriate and will be used. New files will be added to `backend/src/models/` (for `SyncJob`), `backend/src/services/` (for `CurrentSyncJobManager`), and `backend/src/api/` (for the new status endpoint and modifications to existing sync endpoints).
+
+## Complexity Tracking
+
+N/A