perf(round25): in-place encrypted decrypt, dedup hash move, dead folder-Query, playlist N+1 fold, contact vcard over-fetch

Five benchmark-gated optimizations from a fresh six-way audit (benches/ROUND25.md),
each with a BEFORE/AFTER gate that rolls back if AFTER does not beat BEFORE:

- M1 EncryptedBlobBackend::decrypt_bytes: replace split_off (a fresh Vec + full
  ciphertext memcpy on every decrypted chunk, contradicting its own "in place"
  doc) with in-place detached decrypt + a zero-copy Bytes::slice past the nonce.
  Peak RAM per read drops from ~2x to ~1x the payload (-262KB/op at 256KiB;
  scales with blob size). Plaintext byte-identical; tamper/wrong-key tests pass.
- M2 delta commit: move-unzip the owned chunk list instead of a third
  per-occurrence hash clone (-4000 allocs on a 4000-chunk commit).
- M3 folder ZIP download: drop the dead Query<HashMap> extractor it never read
  (byte-identical response; 5->0 allocs/request).
- Q1 public-playlist listing: fold the per-playlist COUNT(*) N+1 into one
  LEFT JOIN ... GROUP BY via a new inherent repo method (101 -> 1 round-trips,
  36x wall on a 100-playlist page).
- Q2 contact REST listings (paginated/search/by-group): stop over-fetching the
  multi-KB vcard TEXT the ContactDto discards, via a shared lite row mapper and
  narrowed SELECTs (6.4x wall on 1000 contacts with 8KiB vcards). The whole-book
  vCard export and CardDAV sync paths keep the column.

Adds bench_round25_micro (counting allocator tracking count+bytes) and
bench_round25_queries (live Postgres), both with equivalence gates and a
rollback exit(1). Verified: cargo fmt clean, cargo clippy -D warnings clean,
cargo test --lib --features bench = 529 passed / 0 failed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L8gs91AhmazoxMsDcNk3KT

Cargo.toml

@@ -354,6 +354,27 @@ name = "bench_micro_allocs"
 path = "examples/bench_micro_allocs.rs"
 required-features = ["bench"]
 
+# Round-25 battery ────────────────────────────────────────────────────────────
+
+# Round-25 CPU/alloc/RAM micro-pack (no Postgres) — deterministic alloc+bytes
+# gates: EncryptedBlobBackend::decrypt_bytes split_off full copy → in-place
+# detached decrypt + zero-copy slice (M1, the RAM headline); delta-commit
+# chunk-hash list third clone → move-unzip (M2); folder download dead
+# Query<HashMap> extractor removal (M3).
+[[example]]
+name = "bench_round25_micro"
+path = "examples/bench_round25_micro.rs"
+required-features = ["bench"]
+
+# Round-25 PG query-shape pack — public-playlist listing 1+N COUNT round-trips
+# → one LEFT JOIN GROUP BY (Q1); contact REST listings dropping the over-fetched
+# multi-KB vcard TEXT the ContactDto discards (Q2). Needs the dev Postgres up
+# (reads DATABASE_URL from .env).
+[[example]]
+name = "bench_round25_queries"
+path = "examples/bench_round25_queries.rs"
+required-features = ["bench"]
+
 # Round-24 battery ────────────────────────────────────────────────────────────
 
 # Round-24 download_zip authz+metadata N+1 → batch, VALIDATED. The per-file