Tracing: DAO layer + handler spans on tracing, drop all Context params (#141)

trace_db_call no longer takes an OpenTelemetry Context: it opens a
db.<query_type>.<operation> span (same name via otel.name, same
db.query_type / db.operation attrs) on the caller's ambient tracing span
and runs the DAO body inside it. The cx / ctx / context parameter is gone
from every DAO trait method, impl and call site, and from the helpers and
background drains that only threaded it.

The remaining request-handler spans (files, tags, faces, image, video,
favorites, duplicates, memories) move to #[instrument]; the
Context::current_with_span / with_remote_span_context plumbing is gone, as
is extract_context_from_request (the tracing-actix-web root span covers
it). otel::set_span_attributes replaces BoxedSpan::set_attributes.

Background-job raw spans (thumbnails, video actors) are left for #142.

tests/otel_db_spans.rs pins name, attributes, status and nesting (across
an instrumented spawn); otel_traceparent now uses an #[instrument]
handler. CLAUDE.md documents the tracing conventions.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ai/daily_summary_job.rs

@@ -232,12 +232,8 @@ pub async fn generate_daily_summaries(
         // Check if summary already exists
         {
             let mut dao = summary_dao.lock().expect("Unable to lock DailySummaryDao");
-            let otel_context = opentelemetry::Context::new();
 
-            if dao
-                .summary_exists(&otel_context, &date_str, contact)
-                .unwrap_or(false)
-            {
+            if dao.summary_exists(&date_str, contact).unwrap_or(false) {
                 skipped += 1;
                 if idx % 10 == 0 {
                     log::info!(
@@ -366,11 +362,10 @@ async fn generate_and_store_daily_summary(
     };
 
     // DAO calls still take an explicit OTel context (#141).
-    let child_cx = span.context();
 
     let mut dao = summary_dao.lock().expect("Unable to lock DailySummaryDao");
     let result = dao
-        .store_summary(&child_cx, insert)
+        .store_summary(insert)
         .map_err(|e| anyhow::anyhow!("Failed to store summary: {:?}", e));
 
     match &result {