Prerelease 1.49.0: embedded apps

[sfc-gh-dmatthews]

📚 Context

Three new embedded apps for version 1.49.0

🧠 Description of Changes

• Sparklines for st.metric
• Directory upload
• Missing basic toast example

Contribution License Agreement

By submitting this pull request you agree that all contributions to this project are made under the Apache 2.0 license.

[Copilot]

Pull Request Overview

This pull request prepares version 1.49.0 by adding three new embedded apps and updating dependency requirements to use nightly builds for testing.

• Adds sparklines functionality to st.metric with chart visualization options
• Introduces directory upload capability for file uploader widget
• Includes a basic toast notification example

Reviewed Changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 2 comments.

File	Description
python/api-examples-source/metric.example5.py	New example demonstrating st.metric with sparklines (line, area, bar charts)
python/api-examples-source/widget.file_uploader_directory.py	New example showing directory upload functionality for file uploader
python/api-examples-source/status.toast.py	New basic example for toast notifications
Multiple requirements.txt files	Updated streamlit dependency from >=1.48.0 to streamlit-nightly

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[lukasmasuch]

LGTM 👍