chore: cargo fmt + clippy --fix sweep across the crate

Pure mechanical cleanup of accumulated drift in files outside the
HLS-content-hash branch's main change set. No behavior change.

- `cargo fmt` on every previously-misformatted file
  (`ai/insight_generator.rs`, `database/knowledge_dao.rs`,
  `faces.rs`, `knowledge.rs`, `libraries.rs`).
- `cargo clippy --fix`:
  - `needless_borrow`: `&library` → `library` in `handlers/image.rs`
    (two sites in the photo-listing path).
- Manual clippy pass for warnings clippy emits but can't auto-apply:
  - `field_reassign_with_default` in `database/reconcile.rs::run` —
    consolidated into a struct-literal initializer.
  - `needless_range_loop` in `database/knowledge_dao.rs::union_perceptual_tags`
    — inner `for b in (a+1)..indices.len() { let ib = indices[b]; ... }`
    becomes `for &ib in &indices[a + 1..] { ... }`.
  - Doc-list indentation: continuation lines under nested bullets in
    `database/mod.rs::get_memories_in_window` and
    `database/knowledge_dao.rs::build_entity_graph` realigned to the
    list-item content column.

Deliberately not touched (each deserves its own focused commit, with
testing, rather than getting bundled into a sweep):
- 4× `deprecated count_distinct` in `faces.rs` — diesel API migration
  to `AggregateExpressionMethods::aggregate_distinct` may shift result
  types; needs verification against the existing stats queries.
- `await_holding_lock` in `knowledge.rs:807` — `std::sync::Mutex` held
  across `ollama.generate(...).await`. Genuine concurrency bug; fix
  requires understanding the surrounding flow before just dropping
  the guard.
- 2× `type_complexity` in `database/mod.rs` — cosmetic, would need a
  `type` alias and corresponding callers updated.
- Dead `total_deleted` on `library_maintenance::GcStats` and
  `file_scan::enumerate_indexable_files` — both are public surface
  retained for future use; deletion is a separate decision.

All 707 tests still pass. Release build clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/insight_generator.rs

@@ -4548,7 +4548,10 @@ mod tests {
 
     #[test]
     fn strip_mark_tags_handles_common_patterns() {
-        assert_eq!(InsightGenerator::strip_mark_tags("plain text"), "plain text");
+        assert_eq!(
+            InsightGenerator::strip_mark_tags("plain text"),
+            "plain text"
+        );
         assert_eq!(
             InsightGenerator::strip_mark_tags("…the <mark>lake</mark>…"),
             "…the lake…"