Add CSV and JSON export utilities for PSLab sensor data

[saadiqbal09]

This PR adds utility functions to export PSLab sensor data
to CSV and JSON formats.

• Useful for IoT data logging and analysis
• Pure Python implementation
• Includes basic pytest-based tests
• No hardware required

This improves data usability for PSLab users.

Summary by Sourcery

Add utility module for exporting PSLab sensor data to common file formats.

New Features:

• Introduce CSV export helper for writing lists of dictionaries to files with headers.
• Introduce JSON export helper for serializing data collections to formatted JSON files.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Adds simple CSV and JSON export utilities for PSLab sensor data, implemented as filesystem-based helper functions with minimal validation and accompanying I/O behavior.

Sequence diagram for CSV and JSON export utility interactions

sequenceDiagram
    actor Caller
    participant data_export_module
    participant csv_module
    participant json_module
    participant FileSystem

    Caller ->> data_export_module: export_to_csv(data, filename)
    alt data is empty
        data_export_module -->> Caller: return
    else data is not empty
        data_export_module ->> FileSystem: open(filename, write, newline empty)
        FileSystem -->> data_export_module: file_handle
        data_export_module ->> csv_module: DictWriter(file_handle, fieldnames from data[0].keys())
        csv_module -->> data_export_module: writer
        data_export_module ->> writer: writeheader()
        data_export_module ->> writer: writerows(data)
        data_export_module ->> FileSystem: close(file_handle)
        data_export_module -->> Caller: return
    end

    Caller ->> data_export_module: export_to_json(data, filename)
    data_export_module ->> FileSystem: open(filename, write)
    FileSystem -->> data_export_module: file_handle
    data_export_module ->> json_module: dump(data, file_handle, indent 4)
    json_module -->> data_export_module: complete
    data_export_module ->> FileSystem: close(file_handle)
    data_export_module -->> Caller: return

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Flow diagram for CSV and JSON data export utilities

flowchart TD
    A["Start"] --> B["Caller invokes export_to_csv or export_to_json with data and filename"]

    B --> C{"Function selected"}
    C --> D["export_to_csv(data, filename)"]
    C --> H["export_to_json(data, filename)"]

    %% CSV path
    D --> E{"Is data empty"}
    E --> F["Return without creating file"]
    E --> G["Open filename for write with newline empty using csv module"]
    G --> I["Create DictWriter with fieldnames from first dict keys"]
    I --> J["Write header row"]
    J --> K["Write all data rows"]
    K --> L["Close file"]
    L --> M["End"]
    F --> M

    %% JSON path
    H --> N["Open filename for write"]
    N --> O["Use json module to dump data with indent 4"]
    O --> P["Close file"]
    P --> M

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File-Level Changes

Change	Details	Files
Introduce CSV export helper for list-of-dict sensor data.	Define export_to_csv(data, filename) that expects a non-empty list of dictionaries. Return early without creating a file when data is falsy. Write CSV using csv.DictWriter with fieldnames derived from the keys of the first element. Always emit a header row followed by one row per dict in the input list.	pslab/utils/data_export.py
Introduce JSON export helper for arbitrary serializable sensor data.	Define export_to_json(data, filename) to write JSON to disk. Use json.dump with a fixed indentation level for pretty-printed output. Assume data is JSON-serializable and do not perform additional validation.	pslab/utils/data_export.py

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• Consider making export_to_csv behavior explicit for empty data (e.g., create an empty file with just a header, or raise a clear error) rather than silently returning, so callers can rely on a predictable outcome.
• It may be useful for both export_to_csv and export_to_json to accept a file-like object in addition to a filename, which would make them easier to use in memory-only or web/CLI contexts.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Consider making `export_to_csv` behavior explicit for empty `data` (e.g., create an empty file with just a header, or raise a clear error) rather than silently returning, so callers can rely on a predictable outcome.
- It may be useful for both `export_to_csv` and `export_to_json` to accept a file-like object in addition to a filename, which would make them easier to use in memory-only or web/CLI contexts.

## Individual Comments

### Comment 1
<location> `pslab/utils/data_export.py:11` </location>
<code_context>
+import csv
+import json
+
+def export_to_csv(data, filename):
+    """
+    data: list of dictionaries
</code_context>

<issue_to_address>
**suggestion (bug_risk):** Consider adding an explicit encoding when opening the CSV file.

Relying on the platform default encoding can cause failures or inconsistent results on different systems, particularly with non-ASCII data. Please specify an explicit encoding (e.g. `encoding="utf-8"`) for consistent behavior.

```suggestion
    with open(filename, "w", newline="", encoding="utf-8") as f:
```
</issue_to_address>

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