perf: round 20 — iCal/vCard parse allocs, owned-DTO moves, Result-collect pre-size, NC etag/favorites emit

Benchmark-gated (benches/ROUND20.md), same rule as rounds 2-19: every change
ships with a BEFORE/AFTER counting-allocator micro-benchmark and a byte-value
equivalence gate; a non-winning AFTER is rolled back (never applied). The
rollback rule is encoded in the harness (GATE FAIL exit). All 8 sections pass.

Reproduce: cargo run --release --features bench --example bench_round20_micro

- A1 CalendarEvent iCal parse: replace the throwaway per-property
  HashMap<String,Vec<String>> (DTSTART/DTEND/RECURRENCE-ID) with a direct
  VALUE=DATE scan; prop_with_params kept #[cfg(test)] (6->2 allocs/event, 4.2x)
- A2 UserDto::from: add User::into_parts and MOVE image (<=512 KiB data URI)
  + ui_preferences JSON instead of cloning on every /api/auth/me (27->14 allocs)
- A3 parse_vcard: drop the per-line to_ascii_uppercase copy + the lines Vec;
  promote ascii_ci_contains to common::text and share it (8->1 allocs/contact)
- A4 Calendar/AddressBook DTO: into_parts move incl. custom_properties map (18->10)
- I1 file-listing repos: collect::<Result<Vec>>() size-hints to 0 and grows from
  capacity 0; pre-size with Vec::with_capacity (8->1 container reallocs, 4 sites)
- I4 plaintext_stream: lazy emit iterator instead of eager Vec collect (43x wall)
- C1 NC write_etag_element: borrowed pre-escaped quote events, no owned quoted
  String/escape re-alloc; byte-identical output (3->0 allocs/PROPFIND row)
- C3 NC favorites REPORT: map.remove() move instead of get().clone() (~7 allocs/fav)

Deferred (documented in ROUND20.md): NC oc:id/trashbin buffer reuse, I1 sibling
CardDAV/CalDAV listing paths, Contact JSONB Json<Vec<_>> decode, dedup
settle_batch &str bind, and a fast DoS-resistant hasher for hot trusted-key maps
(needs a dependency decision).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JsJjcVX9RoN96DMa35Wqzd

src/application/dtos/user_dto.rs

@@ -75,27 +75,37 @@ pub struct UserDto {
 
 impl From<User> for UserDto {
     fn from(user: User) -> Self {
+        // `user` is owned and dropped here, so every owned field is MOVED out
+        // via `into_parts` rather than cloned through the borrowing accessors —
+        // the accessor form deep-cloned `image` (a data URI up to 512 KiB) and
+        // the whole `ui_preferences` JSON tree on every `/api/auth/me` and admin
+        // user listing (benches/ROUND20.md §A2). The two derived values read the
+        // entity before the move.
+        let role = format!("{}", user.role());
+        let can_edit_image = !user.is_oidc_user();
+        let p = user.into_parts();
         Self {
-            id: user.id().to_string(),
-            username: user.username().map(str::to_string),
-            email: user.email().to_string(),
-            role: format!("{}", user.role()),
-            storage_quota_bytes: user.storage_quota_bytes(),
-            storage_used_bytes: user.storage_used_bytes(),
-            created_at: user.created_at(),
-            updated_at: user.updated_at(),
-            last_login_at: user.last_login_at(),
-            active: user.is_active(),
-            auth_provider: user.oidc_provider().unwrap_or("local").to_string(),
-            image: user.image().map(|s| s.to_string()),
-            can_edit_image: !user.is_oidc_user(),
-            is_external: user.is_external(),
-            given_name: user.given_name().map(str::to_string),
-            family_name: user.family_name().map(str::to_string),
-            email_verified_at: user.email_verified_at(),
-            preferred_locale: user.preferred_locale().map(str::to_string),
-            notify_on_share: user.notify_on_share(),
-            ui_preferences: user.ui_preferences().clone(),
+            id: p.id.to_string(),
+            username: p.username,
+            email: p.email,
+            role,
+            storage_quota_bytes: p.storage_quota_bytes,
+            storage_used_bytes: p.storage_used_bytes,
+            created_at: p.created_at,
+            updated_at: p.updated_at,
+            last_login_at: p.last_login_at,
+            active: p.active,
+            // Some(provider) moves the String; None still allocates "local".
+            auth_provider: p.oidc_provider.unwrap_or_else(|| "local".to_string()),
+            image: p.image,
+            can_edit_image,
+            is_external: p.is_external,
+            given_name: p.given_name,
+            family_name: p.family_name,
+            email_verified_at: p.email_verified_at,
+            preferred_locale: p.preferred_locale,
+            notify_on_share: p.notify_on_share,
+            ui_preferences: p.ui_preferences,
         }
     }
 }