fix: repair DashboardState.__init__ (my prior commit orphaned _backtest_lock)

The self-heal commit (a00f967) inserted the _research method INSIDE __init__ at
method-body indent, truncating it so _change_signal/_backtest_lock/_backtest_
cache never got set -> AttributeError on backtest. Moved _research to a sibling
method; __init__ now sets all attrs. Two chart/sparkline tests updated: a None
research_con now REOPENS lazily, so 'no research db attached' is reached only
when the reopen also fails (they monkeypatch open to fail). 22 api tests green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

api/main.py

@@ -257,6 +257,13 @@ class DashboardState:
         self.watch_inject = watch_inject
         self._lock = threading.Lock()
         self._research_lock = threading.Lock()
+        # lazily-built, process-wide SSE change signal (shared by all clients)
+        self._change_signal: _ChangeSignal | None = None
+        # backtest replay cache (plan 015) — a DEDICATED lock, not self._lock,
+        # so a slow replay (10-30s) never blocks the live snapshot/SSE path.
+        # key = (since, until, repr(settings)) -> (result, monotonic timestamp).
+        self._backtest_lock = threading.Lock()
+        self._backtest_cache: dict = {}
 
     def _research(self):
         """The research DB connection, opened LAZILY and self-healing. It used
@@ -276,13 +283,6 @@ class DashboardState:
                     logger.warning("research DB open failed (charts empty): %s", exc)
                     self.research_con = None
         return self.research_con
-        # lazily-built, process-wide SSE change signal (shared by all clients)
-        self._change_signal: _ChangeSignal | None = None
-        # backtest replay cache (plan 015) — a DEDICATED lock, not self._lock,
-        # so a slow replay (10-30s) never blocks the live snapshot/SSE path.
-        # key = (since, until, repr(settings)) -> (result, monotonic timestamp).
-        self._backtest_lock = threading.Lock()
-        self._backtest_cache: dict = {}
 
     def change_stamp(self):
         """SSE change token from the shared once-per-second signal (see _ChangeSignal)."""