feat: Initial implementation of FitTrack Report Generator

This commit introduces the initial version of the FitTrack Report Generator, a FastAPI application for analyzing workout files.

Key features include:
- Parsing of FIT, TCX, and GPX workout files.
- Analysis of power, heart rate, speed, and elevation data.
- Generation of summary reports and charts.
- REST API for single and batch workout analysis.

The project structure has been set up with a `src` directory for core logic, an `api` directory for the FastAPI application, and a `tests` directory for unit, integration, and contract tests.

The development workflow is configured to use Docker and modern Python tooling.

specs/001-create-a-new/data-model.md

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+# Data Model
+
+## Entities
+
+### User
+- **Description**: Represents a user of the system, primarily for storing personalized settings.
+- **Fields**:
+    - `id`: Unique identifier (e.g., UUID)
+    - `ftp_value`: Configured Functional Threshold Power (float, nullable, default value if null)
+- **Relationships**: One-to-many with `WorkoutAnalysis` (a user can have multiple analyses).
+- **Validation Rules**: `ftp_value` must be a positive number if set.
+
+### WorkoutAnalysis
+- **Description**: Represents the result of analyzing a single workout file. This entity links a user to their analyzed workout data.
+- **Fields**:
+    - `id`: Unique identifier (e.g., UUID)
+    - `user_id`: Foreign key to `User.id`
+    - `file_name`: Original name of the workout file (string)
+    - `analysis_date`: Timestamp of when the analysis was performed (datetime)
+    - `status`: Status of the analysis (e.g., 'completed', 'failed', 'processing')
+    - `summary_metrics`: JSONB field for storing overall workout summary metrics (e.g., total distance, duration, average speed, etc.)
+    - `report_path`: Path to the generated report (string)
+    - `chart_paths`: JSONB field for storing paths to generated charts (e.g., `{'power_curve': '/path/to/chart.png'}`)
+- **Relationships**: Many-to-one with `User`.
+
+### WorkoutData (Conceptual/In-Memory Structure)
+- **Description**: Represents the complete raw and processed data for a single workout session. This is primarily an in-memory object during analysis and its key components are persisted in `WorkoutAnalysis`.
+- **Fields**:
+    - `metadata`: `WorkoutMetadata` object
+    - `time_series_data`: Pandas DataFrame containing raw time-series data (e.g., timestamp, power, heart rate, speed, elevation)
+    - `power_data`: `PowerData` object
+    - `heart_rate_data`: `HeartRateData` object
+    - `speed_data`: `SpeedData` object (derived from time-series)
+    - `elevation_data`: `ElevationData` object (derived from time-series)
+
+### WorkoutMetadata
+- **Description**: Metadata extracted from the workout file.
+- **Fields**:
+    - `start_time`: Datetime of workout start
+    - `duration`: Total duration (timedelta or seconds)
+    - `device`: Device used for recording (string)
+    - `file_type`: Original file type (e.g., 'FIT', 'TCX', 'GPX')
+
+### PowerData
+- **Description**: Contains all power-related analysis results.
+- **Fields**:
+    - `raw_power_stream`: List of power values
+    - `average_power`: Float
+    - `normalized_power`: Float
+    - `intensity_factor`: Float
+    - `training_stress_score`: Float
+    - `zone_distribution`: Dictionary/JSONB of time spent in each power zone
+
+### HeartRateData
+- **Description**: Contains all heart-rate-related analysis results.
+- **Fields**:
+    - `raw_hr_stream`: List of heart rate values
+    - `average_hr`: Float
+    - `max_hr`: Integer
+    - `zone_distribution`: Dictionary/JSONB of time spent in each heart rate zone
+
+### ZoneCalculator (Utility)
+- **Description**: A utility class/module for defining and calculating training zones based on user-specific thresholds (like FTP) or default values.
+- **Fields**: (Methods for calculation, not data fields)
+    - `calculate_power_zones(ftp, max_power)`
+    - `calculate_heart_rate_zones(max_hr)`