Stop cache eviction in progress at shutdown (closes #102)

StartEviction runs the eviction goroutine with its own context, which
StopEviction cancels in place of the old stop channel, so a pass in
progress stops at its next database call, file, row or eviction
candidate instead of running to completion. StopEviction takes a
context: when it ends before the goroutine exits, StopEviction stops
waiting and returns an error wrapping it. The handlers' stop hook
passes fx's stop context, so an eviction still running at fx's stop
deadline fails the stop and the exit code is 1. The contextcheck
suppression on the start hook stays, with a one-line reason: the loop
outlives OnStart.

Model: opus-5-5

internal/handlers/handlers.go

@@ -58,23 +58,16 @@ func New(lc fx.Lifecycle, params Params) (*Handlers, error) {
 	}
 
 	lc.Append(fx.Hook{
-		// The eviction goroutine must outlive OnStart, so it cannot
-		// inherit this hook's context. It makes its own instead, which
-		// leaves it uncancellable: an in-flight pass runs to completion
-		// during OnStop regardless of the shutdown deadline. Making the
-		// loop cancellable changes shutdown semantics and is tracked
-		// separately in issue #102, rather than being folded into the
-		// lint-conformance change that surfaced it.
-		//nolint:contextcheck // see issue #102
+		//nolint:contextcheck // the eviction loop outlives OnStart; OnStop cancels it
 		OnStart: func(_ context.Context) error {
 			return s.initImageService()
 		},
-		OnStop: func(_ context.Context) error {
-			if s.imgCache != nil {
-				s.imgCache.StopEviction()
+		OnStop: func(ctx context.Context) error {
+			if s.imgCache == nil {
+				return nil
 			}
 
-			return nil
+			return s.imgCache.StopEviction(ctx)
 		},
 	})