refac(telemetry): drop deprecated semconv SpanAttributes subclass (#25784)

constants.py subclassed opentelemetry.semconv.trace.SpanAttributes, which
is deprecated since semconv 1.25.0 (emits a DeprecationWarning; the pinned
0.63b1 has it live). Source the legacy span-attribute keys from the
non-deprecated _incubating attribute modules instead:
  http.url / http.method / http.status_code  <- _incubating http_attributes
  db.name / db.statement / db.operation      <- _incubating db_attributes
The stable http module renamed these (http.request.method, ...), so only
the incubating module preserves the original values. Custom keys
(db.instance/type/ip/port, error.*, result.*) stay literals.

Verified: emitted attribute keys are byte-identical before/after for every
key instrumentors.py reads, and importing constants no longer emits a
DeprecationWarning.

backend/open_webui/utils/telemetry/constants.py

@@ -1,4 +1,9 @@
-from opentelemetry.semconv.trace import SpanAttributes as _SpanAttributes
+from opentelemetry.semconv._incubating.attributes import (
+    db_attributes as _db,
+)
+from opentelemetry.semconv._incubating.attributes import (
+    http_attributes as _http,
+)
 
 # Span Tags
 SPAN_DB_TYPE = 'mysql'
@@ -9,11 +14,29 @@ SPAN_SQL_EXPLAIN = 'explain'
 SPAN_ERROR_TYPE = 'error'
 
 
-class SpanAttributes(_SpanAttributes):
+class SpanAttributes:
-    """
+    """Span attribute keys used by the telemetry instrumentors.
-    Span Attributes
+
+    Legacy semconv keys (http.* and db.*) are sourced from the `_incubating`
+    attribute modules, which still define these exact string values.
+    `opentelemetry.semconv.trace.SpanAttributes` (previously subclassed here)
+    is deprecated since semconv 1.25.0, and the *stable* http module renamed
+    the keys (e.g. `http.request.method`), so only the incubating module keeps
+    the original `http.method` / `http.url` / `http.status_code` / `db.*` values.
+    Sourcing from it keeps emitted span attribute keys unchanged.
     """
 
+    # HTTP — legacy keys retained in the incubating module
+    HTTP_URL = _http.HTTP_URL  # 'http.url'
+    HTTP_METHOD = _http.HTTP_METHOD  # 'http.method'
+    HTTP_STATUS_CODE = _http.HTTP_STATUS_CODE  # 'http.status_code'
+
+    # DB — incubating semconv keys
+    DB_NAME = _db.DB_NAME  # 'db.name'
+    DB_STATEMENT = _db.DB_STATEMENT  # 'db.statement'
+    DB_OPERATION = _db.DB_OPERATION  # 'db.operation'
+
+    # Open WebUI custom keys (not part of semconv)
     DB_INSTANCE = 'db.instance'
     DB_TYPE = 'db.type'
     DB_IP = 'db.ip'