refactor(notes): remove legacy whole-document saves; all block changes go through sync

Phase 5 of the collaboration plan:
- Remove PATCH /documents/{id}/blocks, PatchDocumentBlocks, the
  DOC_BLOCKS_PATCHED event and its types, FlushDocumentState and
  LoadDocumentState. PUT /documents/{id} rejects blocks (400) and only
  changes title, icon, folder and pin; editors may now change title/icon.
- The to-do overview ticks via a single operation on /docs/{id}/sync
  (new skipLog flag). Task links set the block tick with a targeted
  operation and notify open editors; creating a linked task needs edit
  rights.
- Keep the three share tables: DocRole already decides centrally, and
  rewriting the visibility queries would only add risk (documented in plan).
- Tests adapted to the new paths; share e2e test now also ticks a to-do in
  the overview.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/domain/models.go

@@ -309,25 +309,6 @@ func CompileBlocksToMarkdown(blocks []DocumentBlock) string {
 	return sb.String()
 }
 
-type DocBlocksPatchRequest struct {
-	Upserted   []DocumentBlock `json:"upserted,omitempty"`
-	DeletedIDs []string        `json:"deletedIds,omitempty"`
-	BlockOrder []string        `json:"blockOrder,omitempty"`
-	Title      *string         `json:"title,omitempty"`
-	Icon       *string         `json:"icon,omitempty"`
-}
-
-type DocBlocksPatchEvent struct {
-	DocID      string          `json:"docId"`
-	Upserted   []DocumentBlock `json:"upserted,omitempty"`
-	DeletedIDs []string        `json:"deletedIds,omitempty"`
-	BlockOrder []string        `json:"blockOrder,omitempty"`
-	Title      *string         `json:"title,omitempty"`
-	Icon       *string         `json:"icon,omitempty"`
-	UpdatedBy  string          `json:"updatedBy"`
-	UpdatedAt  string          `json:"updatedAt"`
-}
-
 type DocShare struct {
 	ID          string `json:"id"`
 	DocID       string `json:"docId"`