perf: round 5 — CalDAV cursor streaming, SPA interning gaps, NC href prefix, per-request micro-allocs

Seven benchmark-gated changes (benches/ROUND5.md; BEFORE/AFTER bench +
equivalence gate each, rollback rule as ROUND2-4 — two intermediate
CalDAV shapes measured worse and were themselves rolled back before
shipping):

- CalDAV whole-calendar responses (REPORT no-range/sync-collection,
  depth-1 collection PROPFIND, .ics GET): buffered double-residency →
  ONE window-ordered scan (MIN(start_time) OVER (PARTITION BY ical_uid))
  streamed through a PG cursor, pages cut at UID boundaries. TTFB
  23.3→11.0 ms (2.1x), peak heap 14.2→8.0 MiB at 4k events / 45→24 MiB
  at 12k, wall +9-15% (documented trade, ZIP-streaming class); both
  multistatus and ICS byte-identical to the buffered output. Rejected
  shapes kept in the doc: per-page GROUP-BY keyset (3-4x wall) and
  per-uid ANY hydration (~20 µs/index descent).
- SPA listing interning gaps: folder/recent/favorites resources handlers
  (and the WebDAV pseudo-root) called raw Arc::from per row for the
  closed display set ROUND3 interned — now intern_display/intern_mime,
  4→0 allocs/row, byte-identical Arc contents.
- NC PROPFIND child hrefs: username + parent path encoded once per
  request instead of per child (543→165 ns/row, 13→4 allocs); native
  WebDAV href drops its intermediate encode String.
- suggest enrichment: entity clone + field re-clones per keystroke row →
  consume + move (166.5→126.8 µs/200 rows, 20→7 allocs/row).
- list_readable_by returns the cache's Arc (246→128 ns warm hit, 4→0
  allocs) — deep Vec clone per DAV-selector request removed.
- CardDAV REPORT: borrowed props, reused href buffer, exact-size etag
  quoting (3.04→2.34 ms per 5k-contact getetag poll).
- Auth span records: user_id.to_string() per request ×3 →
  tracing::field::display.

Checks: cargo fmt, clippy --all-features --all-targets -D warnings,
cargo test --workspace (523 passed). Follow-ups (CardDAV streaming,
&[&str] id batches, ::text UUID casts A/B, share-landing join) recorded
in benches/ROUND5.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017aJu9ghvuT8WqC31ZEGTBA

src/interfaces/api/handlers/webdav_handler.rs

@@ -20,6 +20,7 @@ use uuid::Uuid;
 use crate::application::adapters::webdav_adapter::{
     LockInfo, PropFindRequest, PropPatchOp, QualifiedName, WebDavAdapter, is_protected_property,
 };
+use crate::application::dtos::display_helpers::intern_display;
 use crate::application::dtos::file_dto::FileDto;
 use crate::application::dtos::folder_dto::FolderDto;
 use crate::application::ports::authorization_ports::AuthorizationEngine;
@@ -65,10 +66,6 @@ const PATH_SEGMENT_ENCODE_SET: &AsciiSet = &NON_ALPHANUMERIC
     .remove(b'@');
 
 /// Percent-encode a single URI path segment (folder/file name).
-fn encode_path_segment(segment: &str) -> String {
-    utf8_percent_encode(segment, PATH_SEGMENT_ENCODE_SET).to_string()
-}
-
 /// Percent-encode a full slash-separated path, encoding each segment individually.
 pub(crate) fn encode_uri_path(path: &str) -> String {
     use std::fmt::Write as _;
@@ -373,14 +370,14 @@ async fn lookup_drive_selector(
         .list_readable_by(user_id)
         .await
         .map_err(|e| AppError::internal_error(format!("Failed to list drives: {:?}", e)))?;
-    for d in visible {
+    for d in visible.iter() {
         if let Some(uuid) = uuid_opt
             && d.drive.id == uuid
         {
-            return Ok(d);
+            return Ok(d.clone());
         }
         if d.root_folder_name == selector_decoded.as_ref() {
-            return Ok(d);
+            return Ok(d.clone());
         }
     }
     Err(AppError::not_found(format!(
@@ -552,9 +549,9 @@ async fn handle_propfind(
                 created_at: Utc::now().timestamp() as u64,
                 modified_at: Utc::now().timestamp() as u64,
                 is_root: true,
-                icon_class: Arc::from("fas fa-folder"),
-                icon_special_class: Arc::from("folder-icon"),
-                category: Arc::from("Folder"),
+                icon_class: intern_display("fas fa-folder"),
+                icon_special_class: intern_display("folder-icon"),
+                category: intern_display("Folder"),
                 created_by: None,
                 updated_by: None,
             };
@@ -815,7 +812,11 @@ async fn build_streaming_propfind_response(
                     let mut w = Writer::new(&mut chunk);
                     for subfolder in batch.iter() {
                         let child_dead = dead_props_for(&subfolder.id, &subfolder_deads);
-                        let href = format!("{}{}/", base_href, encode_path_segment(&subfolder.name));
+                        let href = format!(
+                            "{}{}/",
+                            base_href,
+                            utf8_percent_encode(&subfolder.name, PATH_SEGMENT_ENCODE_SET)
+                        );
                         WebDavAdapter::write_folder_entry_with_dead_props(&mut w, subfolder, &propfind_request, &href, child_dead, quota)
                             .map_err(|e| std::io::Error::other(e.to_string()))?;
                     }
@@ -856,7 +857,11 @@ async fn build_streaming_propfind_response(
                     let mut w = Writer::new(&mut chunk);
                     for file in batch.iter() {
                         let child_dead = dead_props_for(&file.id, &file_deads);
-                        let href = format!("{}{}", base_href, encode_path_segment(&file.name));
+                        let href = format!(
+                            "{}{}",
+                            base_href,
+                            utf8_percent_encode(&file.name, PATH_SEGMENT_ENCODE_SET)
+                        );
                         WebDavAdapter::write_file_entry_with_dead_props(&mut w, file, &propfind_request, &href, child_dead)
                             .map_err(|e| std::io::Error::other(e.to_string()))?;
                     }