fix: rename cached media files to include extension when missing

[dcalhoun]

Description

Fix CMM-2003.

When a media file's source filename contains spaces (e.g. Samsung screenshots named screenshot_20260327_072755_one ui home5107006954197938205.jpg), Android's path resolution can produce a cached file path that ends with a trailing dot — dropping the file extension entirely.

The existing code in FluxCUtils.mediaModelFromLocalUri() already derives the correct extension from the MIME type and appends it to filename, but the on-disk file path (mFilePath) was left unchanged. Since MediaRSApiRestClient passes mFilePath to wordpress-rs, and reqwest infers the MIME type from the file extension in the path, the upload request was sent with Content-Type: application/octet-stream and a filename without an extension — causing WordPress to reject it with "Sorry, you are not allowed to upload this file type."

This PR adds a step that renames the cached file on disk to include the correct extension when the path doesn't match, keeping mFilePath consistent with mFileName.

Testing instructions

Upload a file with spaces in the filename:

1. On a Samsung device, take a screenshot from an app like Samsung Health or One UI Home (these produce filenames with spaces)
2. Open the WordPress/Jetpack app and navigate to Media
3. Tap + to upload the screenshot

• Verify the upload succeeds without errors

Alternatively, create a test file manually:

1. Using a file manager, create or rename an image file to include spaces (e.g. test file upload.jpg)
2. Share the file to the WordPress/Jetpack app, or upload it via the Media screen

• Verify the upload succeeds without errors

Regression — files without spaces:

1. Upload a media file with a normal filename (no spaces)

• Verify the upload still succeeds as before

[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Android by scanning the QR code below to install the corresponding build.

	App Name	WordPress Android
	Build Type	Debug
	Version	pr22753-23a08d6
	Build Number	1488
	Application ID	org.wordpress.android.prealpha
	Commit	23a08d6
	Installation URL	3chic5ai59o28

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Android by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Android
	Build Type	Debug
	Version	pr22753-23a08d6
	Build Number	1488
	Application ID	com.jetpack.android.prealpha
	Commit	23a08d6
	Installation URL	4mc3ib2vmv9vo

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 37.42%. Comparing base (9839944) to head (23a08d6).
⚠️ Report is 4 commits behind head on trunk.

Files with missing lines	Patch %	Lines
...in/java/org/wordpress/android/util/FluxCUtils.java	0.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            trunk   #22753      +/-   ##
==========================================
- Coverage   37.43%   37.42%   -0.01%     
==========================================
  Files        2320     2320              
  Lines      123589   123598       +9     
  Branches    16757    16760       +3     
==========================================
  Hits        46262    46262              
- Misses      73608    73617       +9     
  Partials     3719     3719              

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[nbradbury]

Worked as described