Add TTL expiry for transient facts

src/config.rs

@@ -12,6 +12,7 @@ pub struct Config {
     pub database: DatabaseConfig,
     pub embedding: EmbeddingConfig,
     pub query: QueryConfig,
+    pub ttl: TtlConfig,
     pub auth: AuthConfig,
 }
 
@@ -55,6 +56,13 @@ pub struct QueryConfig {
     pub text_weight: f32,
 }
 
+/// TTL / expiry configuration
+#[derive(Debug, Clone, Deserialize)]
+pub struct TtlConfig {
+    #[serde(default = "default_cleanup_interval_seconds")]
+    pub cleanup_interval_seconds: u64,
+}
+
 /// Authentication configuration
 #[derive(Debug, Clone, Deserialize)]
 pub struct AuthConfig {
@@ -98,6 +106,7 @@ fn default_model_path() -> String { "models/all-MiniLM-L6-v2".to_string() }
 fn default_embedding_dim() -> usize { 384 }
 fn default_vector_weight() -> f32 { 0.6 }
 fn default_text_weight() -> f32 { 0.4 }
+fn default_cleanup_interval_seconds() -> u64 { 300 }
 fn default_auth_enabled() -> bool { false }
 
 impl Config {
@@ -119,6 +128,11 @@ impl Config {
             // Query settings
             .set_default("query.vector_weight", default_vector_weight() as f64)?
             .set_default("query.text_weight", default_text_weight() as f64)?
+            // TTL settings
+            .set_default(
+                "ttl.cleanup_interval_seconds",
+                default_cleanup_interval_seconds() as i64,
+            )?
             // Auth settings
             .set_default("auth.enabled", default_auth_enabled())?
             // Load from environment with OPENBRAIN_ prefix
@@ -170,6 +184,9 @@ impl Default for Config {
                 vector_weight: default_vector_weight(),
                 text_weight: default_text_weight(),
             },
+            ttl: TtlConfig {
+                cleanup_interval_seconds: default_cleanup_interval_seconds(),
+            },
             auth: AuthConfig {
                 enabled: default_auth_enabled(),
                 api_keys: Vec::new(),