fix(postprocessing): skip UploadReady events without an upload id

[junkerderprovinz]

Description

The posix driver publishes UploadReady for every non-empty file it assimilates from disk, so search, activitylog and clientlog see files that were copied into the storage directly. Those events have no UploadID because there is no upload session. Postprocessing looked the empty ID up in its store, which fails with nats: invalid key, and logged errors for every such file: two lines on 8.0.1, three on main because getPP logs as well.

Postprocessing now returns early for an UploadReady without UploadID, like it already does for a PostprocessingStepFinished from an on-demand scan. The event is still acked. The other consumers don't read UploadID and are unchanged.

A real upload can't hit the new branch. Its UploadReady comes from decomposedfs after PostprocessingFinished and carries the ID that postprocessing used as its store key, so an empty ID never matches a stored upload.

Related Issue

• Fixes postprocessing logs "cannot get upload" for every non-empty file the posix driver assimilates #3606
• Also listed as error 8 in CI. opencloud log contains a lot of errors #2045, and the lines show up in Error Messages after upgrading from 4.0.8 to 7.2.3 #3318.

Motivation and Context

The errors look like failed uploads and bury real ones. On 8.0.1, 300 files copied into a personal space gave 600 error lines at the next start.

How Has This Been Tested?

• test environment: unit tests built with Go 1.26.4 for linux/amd64 and run in an Alpine container. Server built from this branch in the golang:1.26 image and run on data from opencloudeu/opencloud-rolling:latest (8.0.1), posix driver.
• test case 1: new unit test sends an UploadReady without UploadID and expects no error. Without the change it fails with event error: cannot get upload.
• test case 2: new unit test checks that a failed upload is still marked as finished, so events with an ID still reach the store.
• test case 3: the server built from this branch handled 600 UploadReady events for assimilated files without errors (reproduction in postprocessing logs "cannot get upload" for every non-empty file the posix driver assimilates #3606). The files were listed in the space, and a WebDAV upload still went through postprocessing.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation added

Claude Code helped with the investigation, the reproduction and the fix. I reviewed the change and take responsibility for it.

Assisted-by: Claude Code:claude-opus-5-5

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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🟢 Metrics 5 complexity

Metric	Results
Complexity	5

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