fix(cookbook): preserve endpoints across model launches (#6969)

* fix(cookbook): match stale endpoints by launched model, not display name

After registering an LLM endpoint, the Cookbook deleted every other local-*
endpoint with the same display name at a different URL. The display name is
the repo short name, which repos from different orgs share (for example
meta-llama/Llama-3.1-8B-Instruct and unsloth/Llama-3.1-8B-Instruct), so
launching one deleted the endpoint of the other while its server was running.

Match stale endpoints by the full model id they were last launched for,
which is the last entry of their pinned_models. Reusing an endpoint now
moves the launched model to the end of its pins so that entry stays current.

* fix(cookbook): guard endpoint cleanup by serve ownership

Preserve independently launched models instead of sweeping endpoints by display name or mutable model pins.

Bind Cookbook endpoint registrations to their serve sessions and prevent stale watchdogs or scheduled stops from deleting newer registrations.

Reuse the existing endpoint deletion contract to preserve settings, preferences, session cleanup, and cache invalidation.

Cover LLM and image endpoint lifecycle regressions.

---------

Co-authored-by: Alexandre Teixeira <general@alexandreteixeira.dev>

core/database.py

@@ -568,6 +568,7 @@ class ModelEndpoint(TimestampMixin, Base):
     hidden_models = Column(Text, nullable=True)    # JSON list of model IDs that failed probing
     cached_models = Column(Text, nullable=True)    # JSON list of last-known model IDs (avoids probe on list)
     pinned_models = Column(Text, nullable=True)    # JSON list of admin-pinned model IDs (manual, may not appear in /v1/models)
+    cookbook_serve_session_id = Column(String, nullable=True)  # Current Cookbook serve identity
     model_type = Column(String, nullable=True, default="llm")  # "llm" or "image"
     # auto = classify by URL; local = self-hosted server; api/proxy = external
     # OpenAI-compatible API even when reachable through a private/tailnet IP.
@@ -1378,6 +1379,26 @@ def _migrate_add_pinned_models_column():
         except Exception:
             pass
 
+
+def _migrate_add_cookbook_serve_session_id_column():
+    """Bind Cookbook cleanup to the serve session that owns the endpoint."""
+    from sqlalchemy import inspect
+
+    with engine.begin() as conn:
+        columns = {
+            column["name"]
+            for column in inspect(conn).get_columns("model_endpoints")
+        }
+
+        if "cookbook_serve_session_id" not in columns:
+            conn.execute(
+                text(
+                    "ALTER TABLE model_endpoints "
+                    "ADD COLUMN cookbook_serve_session_id VARCHAR"
+                )
+            )
+
+
 def _migrate_add_notes_sort_order():
     """Add sort_order, image_url, repeat columns to notes if they don't exist."""
     import sqlite3
@@ -2390,6 +2411,7 @@ def init_db():
     _migrate_add_hidden_models_column()
     _migrate_add_cached_models_column()
     _migrate_add_pinned_models_column()
+    _migrate_add_cookbook_serve_session_id_column()
     _migrate_add_notes_sort_order()
     _migrate_add_model_type_column()
     _migrate_add_model_endpoint_refresh_columns()