Add config validation and dashboard

Add YAML config loading with validation, env overrides for secrets, and
a web dashboard exposing health, stats, and recent events.

dedup_test.v

@@ -0,0 +1,59 @@
+module main
+
+import sources
+
+fn test_dedup_allows_first_event() {
+	mut d := new_dedup(DedupConfig{
+		enabled:     true
+		ttl_seconds: 300
+		rate_limit:  RateLimitConfig{
+			max_per_minute: 10
+			max_per_source: 30
+		}
+	})
+	event := sources.Event{
+		source:  'generic'
+		name:    'test'
+		topic:   'test'
+		message: 'hello'
+	}
+	assert d.allow(event) == true
+}
+
+fn test_dedup_blocks_duplicate() {
+	mut d := new_dedup(DedupConfig{
+		enabled:     true
+		ttl_seconds: 300
+		rate_limit:  RateLimitConfig{
+			max_per_minute: 10
+			max_per_source: 30
+		}
+	})
+	event := sources.Event{
+		source:  'generic'
+		name:    'test'
+		topic:   'test'
+		message: 'hello'
+	}
+	assert d.allow(event) == true
+	assert d.allow(event) == false
+}
+
+fn test_dedup_disabled() {
+	mut d := new_dedup(DedupConfig{
+		enabled:     false
+		ttl_seconds: 300
+		rate_limit:  RateLimitConfig{
+			max_per_minute: 10
+			max_per_source: 30
+		}
+	})
+	event := sources.Event{
+		source:  'generic'
+		name:    'test'
+		topic:   'test'
+		message: 'hello'
+	}
+	assert d.allow(event) == true
+	assert d.allow(event) == true
+}