refactor(clippy): fix the never-loop error and clear all lint warnings

`cargo clippy --all-targets` was failing on a deny-by-default
`never_loop` in the analysis SSE handler (the `loop` always returned on
the first iteration — the stream `unfold` already re-enters per event),
plus ~28 warnings. All resolved with no behaviour change:

- admin/analysis SSE: drop the dead `loop` wrapper.
- app: match port literals directly instead of `if p == 80` guards.
- repo/user: separate doc list from the following paragraphs.
- repo/upload_history: `sort_by_key(Reverse(..))` over `sort_by`.
- crawler/nav test: construct the error directly (no `unwrap_err` on a
  literal `Err`).
- test helpers: build configs via struct-update syntax instead of
  `Default::default()` + field reassignment; add a type alias for a
  complex audit-row tuple.
- plus the mechanical `deref`/etc. fixes from `cargo clippy --fix`.

Note: not running `cargo fmt` — the backend uses a consistent
hand-formatted style that differs from rustfmt-default across ~110
files, so a blanket reformat would be pure churn.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/repo/upload_history.rs

@@ -110,7 +110,7 @@ pub async fn list_for_user(
         });
     }
     // Newest first; trim to limit after the merge.
-    entries.sort_by(|a, b| b.created_at().cmp(&a.created_at()));
+    entries.sort_by_key(|b| std::cmp::Reverse(b.created_at()));
     entries.truncate(limit as usize);
 
     let (manga_total, chapter_total): (i64, i64) = sqlx::query_as(

backend/src/repo/user.rs

@@ -157,8 +157,10 @@ pub async fn set_is_admin_unchecked(pool: &PgPool, id: Uuid, value: bool) -> App
 /// - If a row already exists: flip `is_admin` to true if needed; **never**
 ///   touch the existing `password_hash`. Lets the operator rotate the
 ///   admin password through the UI without env-var conflict.
+///
 /// Wrapped in a transaction so a concurrent `register` for the same
 /// username can't slip an INSERT between the SELECT and UPDATE/INSERT.
+///
 /// Set `is_admin` on a user with full safety checks: rejects self-demote,
 /// rejects demoting the only remaining admin (under `ADMIN_INVARIANT_LOCK_KEY`
 /// to close the parallel-demote race), and writes an `admin_audit` row