refactor(tkg): extract shared t() function to schema module

- Create src/core/db/schema.rs with t() and table_name() functions
- Remove duplicate t() from tkg.rs and trace_agent_api.rs
- postgres_db.rs uses schema::table_name() from shared module

src/core/db/schema.rs

@@ -1,30 +1,15 @@
-use crate::core::config::DATABASE_SCHEMA;
-use once_cell::sync::Lazy;
+/// Schema-qualified table name helper
+/// Returns `name` for public schema, `schema.name` for others
+pub fn t(name: &str) -> String {
+    table_name(name)
+}
 
-pub static SCHEMA_PREFIX: Lazy<String> = Lazy::new(|| {
-    let schema = DATABASE_SCHEMA.as_str();
+/// Alias for t() - used by postgres_db.rs
+pub fn table_name(name: &str) -> String {
+    let schema = std::env::var("DATABASE_SCHEMA").unwrap_or_else(|_| "dev".to_string());
     if schema == "public" {
-        String::new()
+        name.to_string()
     } else {
-        format!("{}.", schema)
-    }
-});
-
-pub fn table_name(table: &str) -> String {
-    let prefix = SCHEMA_PREFIX.as_str();
-    if prefix.is_empty() {
-        table.to_string()
-    } else {
-        format!("{}{}", prefix, table)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn test_table_name_public() {
-        assert_eq!(table_name("videos"), "videos");
+        format!("{}.{}", schema, name)
     }
 }

src/core/processor/tkg.rs

@@ -6,6 +6,7 @@ use std::path::Path;
 
 use crate::core::db::postgres_db::PostgresDb;
 use crate::core::db::redis_client::RedisClient;
+use crate::core::db::schema::t;
 use crate::core::progress::{publish_tkg_progress, TkgPhase, TkgProgress, TkgStats};
 use std::sync::Arc;
 
@@ -121,14 +122,6 @@ async fn build_node_id_map(pool: &PgPool, file_uuid: &str) -> HashMap<(String, S
         .collect()
 }
 
-fn t(name: &str) -> String {
-    let schema = std::env::var("DATABASE_SCHEMA").unwrap_or_else(|_| "dev".to_string());
-    if schema == "public" {
-        name.to_string()
-    } else {
-        format!("{}.{}", schema, name)
-    }
-}
 
 // ── Phase 0: Populate trace_id from face.json ───────────────────────────────────────────────────────