fix(share): send original file instead of cached thumbnail

[ToteMeiSter]

Problem

Refs #17414

When a picture is not stored on the device, SendShareDialog does not download it. It calls FileOperationsHelper.sendCachedImage, which puts a content://org.nextcloud.imageCache.provider/... URI into ACTION_SEND. That URI is served by DiskLruImageCacheFileProvider, which returns the preview thumbnail from the disk cache, not the original file. The receiving app gets a downscaled PNG instead of the photo.

The provider is exported with android:permission="android.permission.MANAGE_DOCUMENTS". Only the system documents UI holds that permission, so most apps (for example Google Messages, #17414) cannot open the URI at all.

The cached path was added in 2015 (a1bc147849) and extended to the file list in 2016 (d1d99c5e3f) to send a picture without downloading it. Every other file type already goes through SendShareDialogDownloader, which downloads the original and then sends it.

Change

• SendShareDialog.onSendButtonClick: no special case for pictures. A downloaded file is sent at once. A file that is not on the device is downloaded through the host's SendShareDialogDownloader and sent afterwards. A host without a downloader shows "This file can't be sent from here because it isn't on your device yet" instead of closing the dialog without feedback. After this PR no such host is left; the message guards future hosts.
• SendShareAction (new enum) holds this decision, so it is unit-tested without the Android SDK.
• DiskLruImageCacheFileProvider is removed: the class, the manifest entry, the Dagger injector and image_cache_provider_authority in all setup.xml files. Its thumbnail descriptor was also used by DocumentsStorageProvider.openDocumentThumbnail; that code moves into DocumentsStorageProvider unchanged.
• AudioPlayerActivity implements SendShareDialogDownloader through the existing SendShareDownloader, the same way PreviewImageActivity does.
• "Set as" used the same provider for a picture that is not downloaded. FileMenuFilter now hides the entry for such a picture, like "Open with". Every caller of setPictureAs goes through this filter.
• actionbar_send_file was only used by sendCachedImage and is removed.

Hosts of SendShareDialog:

Host	Downloader	Not downloaded file
FileDisplayActivity	yes	downloaded, then sent
PreviewImageActivity	yes	downloaded, then sent
AudioPlayerActivity	yes	downloaded, then sent

Notes

• Related to Sharing with send copy to doesn't work #17619 / fix(sharing): download file before "Send copy to" #17807: after that change a not downloaded file from "Send copy to" goes through SendShareDialog as well. Without this PR a picture would still arrive as the cached thumbnail. The two branches merge without conflicts.
• Behaviour change: sending a not downloaded picture now downloads the full file first, which takes longer and uses more data than the thumbnail did. This is the same behaviour as for every other file type.
• Behaviour change: "Set as" is no longer offered for a not downloaded picture. Privileged system apps (for example the wallpaper picker) could read the old URI, so for them "Set as" used to work with the thumbnail.
• While a not downloaded file is being downloaded for sending, only the system download notification is shown. This is unchanged behaviour for other file types and is left for a follow-up.
• No file overlap with fix(auto-upload): restart folder runs that stay enqueued on rescan #17805, fix(auto-upload): start auto upload right after resuming global upload pause #17806 and fix(sharing): download file before "Send copy to" #17807; trial merge of all four is clean and compiles (unit tests of all three test classes pass on the merge).

How to test

• Unit: SendShareActionTest (4 cases). The existing unit tests pass (jacocoTestGplayDebugUnitTest).
• Instrumented: FileMenuFilterIT.filter_setPictureAs_onlyForDownloadedImages (compiled, not run locally).
• Device: Checked on a HUAWEI Mate X7 (DEL-LX9, EMUI 15.0.0, Android 12) with a test build: works, the original picture is sent instead of the thumbnail.
• Manual steps:
  1. Open the file list, pick a picture that is not downloaded, open "Send/share" and choose an app (for example Google Messages).
  2. The picture is downloaded and the app receives the original file in full resolution.
  3. Repeat from the image preview.
  4. Repeat with a downloaded picture: it is sent at once, as before.
  5. In the audio player, send a file that is not downloaded: it is downloaded and sent.
  6. Open "⋮" on a picture that is not downloaded: "Set as" is not shown.

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI

The change was drafted with Claude Code (Assisted-by: Claude-Code:claude-opus-5-5).

[codecov]

Codecov Report

❌ Patch coverage is 0% with 47 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ud/android/providers/DocumentsStorageProvider.java	0.00%	16 Missing ⚠️
.../com/owncloud/android/ui/dialog/SendShareDialog.kt	0.00%	10 Missing ⚠️
...loud/client/player/ui/audio/AudioPlayerActivity.kt	0.00%	8 Missing ⚠️
.../com/owncloud/android/ui/dialog/SendShareAction.kt	0.00%	8 Missing ⚠️
...cloud/android/ui/helpers/FileOperationsHelper.java	0.00%	4 Missing ⚠️
...ava/com/owncloud/android/files/FileMenuFilter.java	0.00%	0 Missing and 1 partial ⚠️

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