fix(subscriptions): reject concurrent duplicate rules

Fixes #66

internal/model/subscription_identity_test.go

@@ -0,0 +1,45 @@
+package model
+
+import "testing"
+
+func TestSubscriptionIdentityKeyNormalizesEquivalentRules(t *testing.T) {
+	base := Subscription{
+		Name:          " Example Show ",
+		FeedURL:       "site-search://search?keyword=Example",
+		Filter:        " Example.*Show ",
+		MediaType:     "TV",
+		MediaCategory: " 欧美剧 ",
+		SearchMode:    "KEYWORD",
+		Resolution:    "1080P",
+		Effects:       " HDR, Atmos ",
+		ExcludeWords:  " CAM, TS ",
+		WashPriority:  "Balanced",
+		Priority:      50,
+	}
+	equivalent := base
+	equivalent.Name = "example show"
+	equivalent.MediaType = "tv"
+	equivalent.MediaCategory = "欧美剧"
+	equivalent.SearchMode = "keyword"
+	equivalent.Resolution = "1080p"
+	equivalent.Effects = "hdr,atmos"
+	equivalent.ExcludeWords = "cam,ts"
+	equivalent.WashPriority = "balanced"
+	if got, want := SubscriptionIdentityKey(&equivalent), SubscriptionIdentityKey(&base); got != want {
+		t.Fatalf("equivalent keys differ: %s != %s", got, want)
+	}
+
+	differentRule := base
+	differentRule.Resolution = "2160p"
+	if SubscriptionIdentityKey(&differentRule) == SubscriptionIdentityKey(&base) {
+		t.Fatal("different resolution should produce a different identity")
+	}
+
+	displayOnly := base
+	displayOnly.PosterURL = "https://example.test/poster.jpg"
+	displayOnly.Overview = "new overview"
+	displayOnly.TotalEpisodes = 24
+	if SubscriptionIdentityKey(&displayOnly) != SubscriptionIdentityKey(&base) {
+		t.Fatal("display/runtime metadata should not change identity")
+	}
+}