Improve attachment memory safety, downloads, and high-memory alert UX.

Stream large receives to disk with chunk acks to cap renderer RAM, evict
off-screen display blobs, and route exports through a disk-aware download
service. Fix the high-memory dialog (backdrop dismiss, copy, log actions),
allow diagnostics paths in the path jail, and restore persisted image
hydration after reload.

Co-authored-by: Cursor <cursoragent@cursor.com>

toju-app/src/app/domains/attachment/domain/logic/attachment.logic.spec.ts

@@ -58,7 +58,7 @@ describe('attachment logic', () => {
     }, undefined, true)).toBe(false);
   });
 
-  it('streams oversized generic files to disk when the store supports it', () => {
+  it('streams any persistable download to disk when the store supports streaming', () => {
     const capabilities = {
       canStreamToDisk: true,
       canPersistSize: (bytes: number) => bytes <= 256 * 1024 * 1024
@@ -69,6 +69,18 @@ describe('attachment logic', () => {
       mime: 'application/zip',
       filePath: undefined
     }, capabilities)).toBe(true);
+
+    expect(shouldStreamAttachmentReceiveToDisk({
+      size: 3,
+      mime: 'application/zip',
+      filePath: undefined
+    }, capabilities)).toBe(true);
+
+    expect(shouldStreamAttachmentReceiveToDisk({
+      size: 200 * 1024 * 1024,
+      mime: 'application/zip',
+      filePath: '/home/ludde/archive.zip'
+    }, capabilities)).toBe(true);
   });
 
   it('receives browser-sized files in memory when disk streaming is unavailable', () => {