feat: add data freshness indicator with relative time and patient count (Task 5.3)

IMPLEMENTATION_PLAN.md

@@ -242,9 +242,9 @@ Drawer selection → update_drug_selection → app-state store → load_pathway_
 - **Checkpoint**: Loading spinner appears during data fetch, empty state shows message
 
 ### 5.3 Data freshness indicator
-- [ ] Header shows: green dot + "{N} records" + "Last updated: {relative_time}"
-- [ ] Pull from `pathway_refresh_log` via `queries.load_initial_data()`
-- [ ] Format as relative time (e.g., "2h ago", "yesterday")
+- [x] Header shows: green dot + "{N} patients" + "Last updated: {relative_time}"
+- [x] Pull from `pathway_refresh_log` via `queries.load_initial_data()` (uses total_patients from root node as fallback when source_row_count is 0)
+- [x] Format as relative time (e.g., "2h ago", "yesterday")
 - **Checkpoint**: Header shows correct data freshness
 
 ### 5.4 Remove Reflex + final validation

dash_app/callbacks/filters.py

@@ -1,7 +1,39 @@
 """Callbacks for reference data loading and filter state management."""
+from datetime import datetime
 from dash import Input, Output, State, callback, ctx, no_update
 
 
+def _format_relative_time(iso_timestamp: str) -> str:
+    """Format an ISO timestamp as relative time (e.g., '2h ago', 'yesterday')."""
+    if not iso_timestamp:
+        return "Unknown"
+    try:
+        dt = datetime.fromisoformat(iso_timestamp)
+        now = datetime.now()
+        delta = now - dt
+        seconds = int(delta.total_seconds())
+
+        if seconds < 60:
+            return "just now"
+        minutes = seconds // 60
+        if minutes < 60:
+            return f"{minutes}m ago"
+        hours = minutes // 60
+        if hours < 24:
+            return f"{hours}h ago"
+        days = hours // 24
+        if days == 1:
+            return "yesterday"
+        if days < 7:
+            return f"{days}d ago"
+        if days < 30:
+            weeks = days // 7
+            return f"{weeks}w ago"
+        return dt.strftime("%d %b %Y")
+    except (ValueError, TypeError):
+        return iso_timestamp[:10] if len(iso_timestamp) >= 10 else "Unknown"
+
+
 def register_filter_callbacks(app):
     """Register reference data loading and filter state callbacks."""
 
@@ -16,10 +48,18 @@ def register_filter_callbacks(app):
         from dash_app.data.queries import load_initial_data
 
         ref = load_initial_data()
+
         total = ref.get("total_records", 0)
-        record_text = f"{total:,} records" if total else "Data loaded"
+        patients = ref.get("total_patients", 0)
+        if total:
+            record_text = f"{total:,} records"
+        elif patients:
+            record_text = f"{patients:,} patients"
+        else:
+            record_text = "Data loaded"
+
         last_updated = ref.get("last_updated", "")
-        updated_text = last_updated[:10] if last_updated else "Unknown"
+        updated_text = _format_relative_time(last_updated)
 
         return ref, record_text, updated_text
 

src/data_processing/pathway_queries.py

@@ -92,12 +92,24 @@ def load_initial_data(db_path: Path) -> dict:
         """)
         available_trusts = [row[0] for row in cursor.fetchall()]
 
+        # Total patients from default root node (fallback when source_row_count is empty)
+        total_patients = 0
+        if not total_records:
+            cursor.execute("""
+                SELECT value FROM pathway_nodes
+                WHERE level = 0 AND date_filter_id = 'all_6mo' AND chart_type = 'directory'
+                LIMIT 1
+            """)
+            root_row = cursor.fetchone()
+            total_patients = (root_row[0] or 0) if root_row else 0
+
         return {
             "available_drugs": available_drugs,
             "available_directorates": available_directorates,
             "available_indications": available_indications,
             "available_trusts": available_trusts,
             "total_records": total_records,
+            "total_patients": total_patients,
             "last_updated": last_updated,
         }
     except sqlite3.Error as e: