fix: correct import skipped count when manual entries exist

Problem: Import reported all entries as "updated" even when skipped
due to WHERE clause (source != 'manual')

Root cause: RETURNING returns NULL when WHERE clause prevents update,
but code counted NULL as "updated" instead of "skipped"

Fix:
- Check if result is None → skipped (WHERE prevented update)
- Check if xmax = 0 → inserted (new row)
- Otherwise → updated (existing row modified)

Affects:
- vitals_baseline.py: Apple Health import
- blood_pressure.py: Omron import

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/routers/blood_pressure.py

@@ -376,7 +376,10 @@ async def import_omron_csv(
                 ))
 
                 result = cur.fetchone()
-                if result and result['inserted']:
+                if result is None:
+                    # WHERE clause prevented update (manual entry exists)
+                    skipped += 1
+                elif result['inserted']:
                     inserted += 1
                 else:
                     updated += 1

backend/routers/vitals_baseline.py

@@ -357,7 +357,10 @@ async def import_apple_health_baseline(
                 ))
 
                 result = cur.fetchone()
-                if result and result['inserted']:
+                if result is None:
+                    # WHERE clause prevented update (manual entry exists)
+                    skipped += 1
+                elif result['inserted']:
                     inserted += 1
                 else:
                     updated += 1