perf(round29): cache-serve borrow-probe, NC REPORT href buffer, auth per-req allocs, DB over-fetch

Seven behaviour-preserving allocation / copy / bandwidth cuts, each behind a
counting-allocator BEFORE/AFTER gate that exit(1)s unless AFTER allocates
strictly fewer than BEFORE (benches/ROUND29.md, examples/bench_round29_micro.rs).

- [B] Content-cache serve fast path (optimized_inner Tier 1 +
  get_file_range_preloaded — the video-scrub hot path): probe the cache with a
  borrow first and build the owned get_or_load args (quoted-etag / key / id
  Strings) only on a miss, instead of allocating them before every probe and
  discarding them on a hit. 6 -> 0 allocs per cache hit. Splits get_or_load into
  get + load_and_cache so the miss path is not re-probed and the hit/miss stat
  counters stay byte-identical. Also drops the unconditional content_hash/name
  clones that ran for the >=10 MB streaming tier that used neither.
- [A] NextCloud REPORT emit loops: per-row href String (and format! per folder
  row) -> one reused href_buf via nc_href_into / nc_collection_href_into with the
  URL-encoded user computed once per page. 1497 fewer allocs on a 500-row page.
- [C] read_full: a single-frame blob is returned zero-copy instead of a second
  whole-payload memcpy into a fresh BytesMut; multi-frame path unchanged.
- [D] login-lockout key: to_lowercase()+format! -> one pre-sized ASCII buffer
  (non-ASCII keeps str::to_lowercase). 3 -> 1 alloc/req, byte-identical key.
- [E] NC composite-username parse: owned clone/to_string -> &str borrow of the
  already-owned raw_username. 1 -> 0 alloc on the common no-marker path.
- [F] get_contacts_in_group: stop SELECTing the discarded multi-KB vcard column
  (the live method ROUND25 §Q2 missed; ContactDto has no vcard field).
- [G] count_admin_users: add count_users_by_role -> scalar COUNT(*) instead of
  hydrating every admin's full row (incl. up-to-512 KiB avatar + ui_preferences
  JSONB) only to .len() it, on a bootstrap-polled status endpoint.

All seven gates pass; cargo fmt --check and cargo clippy --all-features
--all-targets -D warnings clean. §F/§G additionally validated against a live
PostgreSQL 16 with the full migration set (query validity, result equivalence,
600000 -> 8 byte wire delta on the admin count).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhpDZxSQTAGnAqCHUdtG5N

src/interfaces/nextcloud/report_handler.rs

@@ -24,8 +24,8 @@ use crate::interfaces::api::handlers::webdav_handler::{
 };
 use crate::interfaces::errors::AppError;
 use crate::interfaces::nextcloud::webdav_handler::{
-    batch_resolve_ids, format_oc_id_into, nc_href, nc_id_of, write_file_response,
-    write_folder_response,
+    batch_resolve_ids, format_oc_id_into, nc_collection_href_into, nc_href_into, nc_id_of,
+    write_file_response, write_folder_response,
 };
 
 /// Handle WebDAV REPORT and SEARCH methods for Nextcloud compatibility.
@@ -177,6 +177,12 @@ async fn handle_filter_files(
         // owner-id stays canonical via `&user.username`.
         // One oc:id buffer reused across both emit loops (benches/ROUND27.md §H1).
         let mut oc_buf = String::new();
+        // One href buffer reused across both emit loops, with the URL-encoded
+        // user computed once for the page instead of re-encoded per row — the
+        // reused-buffer shape the PROPFIND child loop already uses
+        // (benches/ROUND29.md §A).
+        let encoded_user = urlencoding::encode(url_user);
+        let mut href_buf = String::new();
         for file in &files {
             // Skip favorites that live outside the caller's chroot
             // (other-drive favorites); reachable via REST if needed.
@@ -189,7 +195,7 @@ async fn handle_filter_files(
                 );
                 continue;
             };
-            let href = nc_href(url_user, subpath);
+            nc_href_into(&mut href_buf, &encoded_user, subpath);
             let fid = nc_id_of(&file_id_map, &file.id);
             let oc_id: Option<&str> = match fid {
                 Some(id) => {
@@ -202,7 +208,7 @@ async fn handle_filter_files(
             write_file_response(
                 &mut xml,
                 file,
-                &href,
+                &href_buf,
                 (fid, oc_id),
                 &user.username,
                 &favorite_ids,
@@ -221,7 +227,7 @@ async fn handle_filter_files(
                 );
                 continue;
             };
-            let href = format!("{}/", nc_href(url_user, subpath));
+            nc_collection_href_into(&mut href_buf, &encoded_user, subpath);
             let fid = nc_id_of(&folder_id_map, &folder.id);
             let oc_id: Option<&str> = match fid {
                 Some(id) => {
@@ -234,7 +240,7 @@ async fn handle_filter_files(
             write_folder_response(
                 &mut xml,
                 folder,
-                &href,
+                &href_buf,
                 (fid, oc_id),
                 &user.username,
                 &favorite_ids,
@@ -334,6 +340,12 @@ async fn handle_search(
         // Files.
         // One oc:id buffer reused across both emit loops (benches/ROUND27.md §H1).
         let mut oc_buf = String::new();
+        // One href buffer reused across both emit loops, with the URL-encoded
+        // user computed once for the page instead of re-encoded per row — the
+        // reused-buffer shape the PROPFIND child loop already uses
+        // (benches/ROUND29.md §A).
+        let encoded_user = urlencoding::encode(url_user);
+        let mut href_buf = String::new();
         for file in &files {
             let Some(subpath) = strip_home_prefix(chroot, &file.path, home_prefix) else {
                 tracing::debug!(
@@ -344,7 +356,7 @@ async fn handle_search(
                 );
                 continue;
             };
-            let href = nc_href(url_user, subpath);
+            nc_href_into(&mut href_buf, &encoded_user, subpath);
             let fid = nc_id_of(&file_id_map, &file.id);
             let oc_id: Option<&str> = match fid {
                 Some(id) => {
@@ -357,7 +369,7 @@ async fn handle_search(
             write_file_response(
                 &mut xml,
                 file,
-                &href,
+                &href_buf,
                 (fid, oc_id),
                 &user.username,
                 &favorite_ids,
@@ -377,7 +389,7 @@ async fn handle_search(
                 );
                 continue;
             };
-            let href = format!("{}/", nc_href(url_user, subpath));
+            nc_collection_href_into(&mut href_buf, &encoded_user, subpath);
             let fid = nc_id_of(&folder_id_map, &folder.id);
             let oc_id: Option<&str> = match fid {
                 Some(id) => {
@@ -390,7 +402,7 @@ async fn handle_search(
             write_folder_response(
                 &mut xml,
                 folder,
-                &href,
+                &href_buf,
                 (fid, oc_id),
                 &user.username,
                 &favorite_ids,