feat(yarn_client): SSL/TLS config for YARN REST connections

Add per-Connection ssl_verify / ssl_ca_bundle plus global defaults so
CDH 5 / on-prem clusters with self-signed certs or custom CA bundles can
be queried without patching code.

- Connection gets ssl_verify (bool|None) and ssl_ca_bundle (str|None)
- Settings gets ssl_verify_default and ssl_ca_bundle_default
- New YarnClientConfig dataclass carries the resolved verify= value
- _request passes verify= through to httpx.request
- All public yarn_client functions now take YarnClientConfig instead of
  a bare yarn_rm_url string; tool call sites resolve the Connection
- SaveConnectionRequest exposes the two new fields

Tests cover per-connection CA bundle, per-connection verify=False,
global default fallback, and connection-not-found error.

tests/unit/test_result_tool.py

@@ -4,17 +4,28 @@ from unittest.mock import patch
 
 import pytest
 
+from spark_executor.core import connection_store
 from spark_executor.core.job_store import JobStore
-from spark_executor.models import Job
+from spark_executor.models import Connection, Job
 from spark_executor.tools import result
+from spark_executor.tools import connections
 
 
-def test_result_returns_parsed_fields():
+def _fresh_stores():
+    store = connection_store.ConnectionStore()
+    connection_store.store = store
+    connections.store = store
+    result.conn_store = store
     result.store = JobStore()
+
+
+def _seed(job_id="abc", app_id="application_1"):
+    _fresh_stores()
+    result.conn_store.save(Connection(name="prod", master="yarn", yarn_rm_url="http://rm:8088"))
     result.store.put(
         Job(
-            job_id="abc",
-            application_id="application_1",
+            job_id=job_id,
+            application_id=app_id,
             script_path="/tmp/j.py",
             queue="default",
             submit_time=datetime(2026, 6, 24),
@@ -22,6 +33,10 @@ def test_result_returns_parsed_fields():
             yarn_rm_url="http://rm:8088",
         )
     )
+
+
+def test_result_returns_parsed_fields():
+    _seed()
     raw = {
         "app": {
             "id": "application_1",
@@ -48,22 +63,13 @@ def test_result_returns_parsed_fields():
     assert out.tracking_url == "http://nm:8088/proxy/application_1"
     assert out.started_time == 1700000000000
     assert out.finished_time == 1700000123000
-    assert m.call_args.args == ("application_1", "http://rm:8088")
+    args = m.call_args.args
+    assert args[0] == "application_1"
+    assert args[1].yarn_rm_url == "http://rm:8088"
 
 
 def test_result_handles_running_job():
-    result.store = JobStore()
-    result.store.put(
-        Job(
-            job_id="running",
-            application_id="application_2",
-            script_path="/tmp/j.py",
-            queue="default",
-            submit_time=datetime(2026, 6, 24),
-            connection="prod",
-            yarn_rm_url="http://rm:8088",
-        )
-    )
+    _seed(job_id="running", app_id="application_2")
     raw = {
         "app": {
             "id": "application_2",
@@ -87,18 +93,7 @@ def test_result_handles_running_job():
 
 
 def test_result_handles_missing_optional_fields():
-    result.store = JobStore()
-    result.store.put(
-        Job(
-            job_id="accepted",
-            application_id="application_3",
-            script_path="/tmp/j.py",
-            queue="default",
-            submit_time=datetime(2026, 6, 24),
-            connection="prod",
-            yarn_rm_url="http://rm:8088",
-        )
-    )
+    _seed(job_id="accepted", app_id="application_3")
     raw = {"app": {"id": "application_3", "state": "ACCEPTED"}}
     import json
 
@@ -118,6 +113,22 @@ def test_result_handles_missing_optional_fields():
 
 
 def test_result_raises_keyerror_for_unknown_job():
-    result.store = JobStore()
+    _fresh_stores()
     with pytest.raises(KeyError, match="Unknown job_id"):
         result.get_job_result("missing")
+
+
+def test_result_raises_when_connection_missing():
+    _fresh_stores()
+    result.store.put(
+        Job(
+            job_id="abc",
+            application_id="application_1",
+            script_path="/tmp/j.py",
+            queue="default",
+            submit_time=datetime(2026, 6, 24),
+            connection="missing",
+        )
+    )
+    with pytest.raises(KeyError, match="Connection not found"):
+        result.get_job_result("abc")