fix: wipe downloaded resources on COMPLETE rescan

[gantoine]

Problem

A COMPLETE rescan never deleted previously downloaded asset files, and the post-scan download steps short-circuit when work appears already done:

• store_media_file always skips when the destination file exists (no overwrite param)
• get_cover / get_manual / get_rom_screenshots only re-download when the source URL changed

So covers, screenshots, manuals, and SS/gamelist/LaunchBox extended media (miximage, bezel, box3d, logo, fanart, video, …) were reused even when a fresh fetch returned a different URL. This defeated the region-priority fix in #3396: the correct region couldn't replace an already-downloaded wrong-region cover/media because the old file was still on disk and path_cover_s still pointed at it.

Separately, when the sole provider of an artwork field was deselected, the on-disk file lingered and the url_* DB columns kept stale values (they're never seeded for COMPLETE, and the priority loops only set fields, never clear them).

Fix

• endpoints/sockets/scan.py — for a COMPLETE rescan of an existing ROM, remove the cover, manual, screenshots, and every extended-media directory before re-fetching, so get_cover/store_media_file pull fresh files.
• handler/scan_handler.py — reset url_cover/url_screenshots/url_manual and the matching path_* fields for COMPLETE rescans before the priority loops run. Stale DB values are now explicitly nulled when no selected source supplies them, rather than relying on session.merge semantics. Clearing for deselected sources falls out as a subset of this behavior.

Testing

DB_HOST=127.0.0.1 uv run pytest tests/endpoints/sockets/test_scan.py tests/handler/filesystem/test_resources_handler.py tests/handler/test_fastapi.py — 102 passed.

🤖 Generated with Claude Code

[github-actions]

Test Results (mariadb)

    1 files  ±0      1 suites  ±0   4m 5s ⏱️ +21s
1 378 tests ±0  1 378 ✅ ±0  0 💤 ±0  0 ❌ ±0 
1 380 runs  ±0  1 380 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit da5675d. ± Comparison against base commit d7c789c.

♻️ This comment has been updated with latest results.

[github-actions]

☂️ Python Coverage

current status: ✅

Overall Coverage

Lines	Covered	Coverage	Threshold	Status
16485	11564	70%	0%	🟢

New Files

No new covered files...

Modified Files

File	Coverage	Status
backend/endpoints/sockets/scan.py	23%	🟢
backend/handler/scan_handler.py	63%	🟢
TOTAL	43%	🟢

updated for commit: da5675d by action🐍

[Copilot]

Pull request overview

This PR fixes COMPLETE rescan behavior so previously downloaded artwork/media doesn’t get reused when metadata providers return updated URLs or when providers are deselected, ensuring “fresh” assets and clearing stale DB URL/path fields.

Changes:

• Reset artwork URL/path fields during COMPLETE rescans so stale values get cleared when no selected source provides them.
• Wipe on-disk downloaded artwork/media directories for existing ROMs during COMPLETE rescans to force re-fetching.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
backend/handler/scan_handler.py	Clears artwork URL/path fields during COMPLETE rescans so stale values don’t persist when no provider supplies them.
backend/endpoints/sockets/scan.py	Deletes existing on-disk artwork/media resources before COMPLETE rescans to prevent reuse of stale files.

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[github-actions]

Test Results (postgresql)

    1 files  ±0      1 suites  ±0   3m 56s ⏱️ -4s
1 378 tests ±0  1 378 ✅ ±0  0 💤 ±0  0 ❌ ±0 
1 380 runs  ±0  1 380 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit da5675d. ± Comparison against base commit d7c789c.

♻️ This comment has been updated with latest results.