merge(frontend): resolve conflicts with main — integrate fileHash feature into panel architecture

Keep the new bottom-panel / AnnotationSidePanel architecture from this branch
while pulling in the documentFileHash / visibleAnnotations filter that was added
on main. Thread documentFileHash through DocumentViewer so outdated-annotation
filtering works end-to-end.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/messages/en.json

@@ -2,6 +2,7 @@
 	"$schema": "https://inlang.com/schema/inlang-message-format",
 	"error_annotation_not_found": "Annotation not found.",
 	"error_annotation_overlap": "The annotation overlaps an existing one.",
+	"annotation_outdated_notice": "Some annotations refer to an earlier file version and are not shown.",
 	"error_document_not_found": "Document not found.",
 	"error_document_no_file": "No file is associated with this document.",
 	"error_file_not_found": "The file could not be found in storage.",
@@ -241,6 +242,10 @@
 	"admin_system_backfill_description": "Creates an initial history entry for all documents that do not have one yet (e.g. imported documents). This ensures that future edits only highlight actually changed fields.",
 	"admin_system_backfill_btn": "Backfill now",
 	"admin_system_backfill_success": "{count} documents were backfilled.",
+	"admin_system_backfill_hashes_heading": "Compute file hashes",
+	"admin_system_backfill_hashes_description": "Computes the SHA-256 hash for all previously uploaded documents that do not have one yet. This ensures annotations are correctly linked to their file version and shown again.",
+	"admin_system_backfill_hashes_btn": "Compute file hashes",
+	"admin_system_backfill_hashes_success": "{count} documents were updated.",
 	"comp_expandable_show_more": "Show more",
 	"comp_expandable_show_less": "Show less",
 	"error_comment_not_found": "The comment could not be found.",