attachments preview overlay, docx/xlsx/odf rendering, composer drag-drop & undo-send UX

Frontend:
- Full-screen attachment preview overlay (AttachmentPreview) for image/pdf/txt
  plus office docs: .docx via docx-preview (rendered live into the sandboxed
  iframe so header/footer VML images survive), .xlsx via xlsx-preview, and
  .odt/.ods/.odp/.odg via a JSZip+DOMParser ODF walker (officeConvert).
- Type-aware attachment icons (green spreadsheet, blue document, red PDF,
  image/archive); new document/image/spreadsheet/print SVGs.
- Composer: drag-drop attachments (body drop inserts images inline, else
  attaches); inserted images are selectable/resizable/deletable (RichTextEditor).
- Undo-send: "Sending…" banner with live "N seconds to Undo" countdown.
- Search result list: pin/archive/delete update correctly; grey-out only for
  search hits; scoped "Search in Trash/Spam".

Backend:
- Search: prefix (search-as-you-type) matching, email-address search, and
  address-first result ordering; Trash/Junk excluded with scoped folder search.
- Attachments: RFC 6266 Content-Disposition for non-ASCII filenames; one-time
  inline image loading.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Rcj3TpydMTzTSmU7kunzf8

backend/tests/search/test_search_api.py

@@ -86,6 +86,8 @@ async def _ingest(
     body: str,
     flags: frozenset[str] = frozenset(),
     attach: bool = False,
+    mailbox_id: uuid.UUID | None = None,
+    special: str = "inbox",
 ) -> None:
     ctx.uid += 1
     m = EmailMessage()
@@ -101,8 +103,8 @@ async def _ingest(
         ctx.session,
         user_id=ctx.user_id,
         account_id=ctx.account_id,
-        mailbox_id=ctx.mailbox_id,
-        mailbox_special_use="inbox",
+        mailbox_id=mailbox_id or ctx.mailbox_id,
+        mailbox_special_use=special,
         remote=RemoteMessage(
             uid=ctx.uid, raw=m.as_bytes(), flags=flags, internal_date=datetime.now(UTC)
         ),
@@ -145,6 +147,25 @@ async def seeded(ctx: Ctx) -> Ctx:
     return ctx
 
 
+async def test_search_excludes_trash_by_default(ctx: Ctx) -> None:
+    # Deleting a message from search results (it moves to Trash) removes it from the
+    # results — search excludes Trash/Junk unless in:trash/in:junk asks for them.
+    from app.models import Mailbox
+
+    await _ingest(ctx, frm="Bob <bob@corp.com>", subject="quarterly zephyr", body="hi")
+    trash = Mailbox(
+        account_id=ctx.account_id, user_id=ctx.user_id, path="Trash", special_use="trash"
+    )
+    ctx.session.add(trash)
+    await ctx.session.flush()
+    await _ingest(
+        ctx, frm="X <x@corp.com>", subject="zephyr in trash", body="bye",
+        mailbox_id=trash.id, special="trash",
+    )
+    assert await _search(ctx, "zephyr") == 1  # inbox only; the trashed one is hidden
+    assert await _search(ctx, "in:trash zephyr") == 1  # explicit -> searches Trash
+
+
 async def test_free_text(seeded: Ctx) -> None:
     assert await _search(seeded, "revenue") == 1
     assert await _search(seeded, "lunch") == 1