fix(sharing): gate falls back to direct ownership before share check

The share-gate I added in Phase B was too strict: it only admitted the
owner via the profiles collection, so any data item whose profile_id
didn't map to a real Profile document (legacy/test data, or a profile_id
the caller used at create time without a backing Profile) got 404'd on
read — even for the item's actual owner. CI caught this:
zk_integration_tests::medication_stored_as_ciphertext_not_plaintext
creates a medication with profile_id="default" (no Profile doc) and
the new get_medication gate returned 404.

Fix: in each list/get data handler, check direct ownership
(user_id == claims.sub, or has own data for the profile) FIRST, and
only fall through to the share-gate if the caller isn't the direct
owner. This preserves the original ownership model AND adds share-
recipient access, without breaking items whose profile_id isn't a real
Profile document.

The share-only path (recipient reading shared data they don't own)
still goes through the gate as before.

backend/src/handlers/appointments.rs

@@ -69,13 +69,23 @@ pub async fn list_appointments(
     let database = state.db.get_database();
     let repo = AppointmentRepository::new(database.collection("appointments"));
 
-    // Share-gate: if a profile_id is specified, resolve the owner (admits the
+    // Resolve the effective owner. If a profile_id is specified, prefer direct
-    // owner or an active share recipient) and query as them. Without a
+    // ownership (the caller's own data for that profile); otherwise fall through
-    // profile_id, return the caller's own data across all their profiles.
+    // to the share-gate (admits an active share recipient). profile_id is a
+    // free-form string at create time and may not map to a Profile document.
     let owner = match &query.profile_id {
         Some(pid) => {
+            let has_own = repo
+                .find_by_user_filtered(&claims.sub, None, Some(pid))
+                .await
+                .map(|v| !v.is_empty())
+                .unwrap_or(false);
+            if has_own {
+                claims.sub.clone()
+            } else {
                 crate::handlers::profile_share::authorize_profile_read(&state, &claims, pid).await?
             }
+        }
         None => claims.sub.clone(),
     };
 
@@ -121,9 +131,12 @@ pub async fn get_appointment(
             ));
         }
     };
-    // Share-gate on the appointment's profile.
+    // Authorization: direct owner (user_id == caller) OR share-gate on the
+    // appointment's profile (admits an active share recipient).
+    if appt.user_id != claims.sub {
         crate::handlers::profile_share::authorize_profile_read(&state, &claims, &appt.profile_id)
             .await?;
+    }
     Ok(Json(appt.into()))
 }
 

backend/src/handlers/health_stats.rs

@@ -90,16 +90,28 @@ pub async fn list_health_stats(
                 .into_response()
         }
     };
-    // Share-gate: if a profile_id is specified, resolve the owner (admits the
+    // Resolve the effective owner. If a profile_id is specified, prefer direct
-    // owner or an active share recipient) and query as them.
+    // ownership (the caller's own data for that profile); otherwise fall through
+    // to the share-gate (admits an active share recipient). profile_id is a
+    // free-form string at create time and may not map to a Profile document.
     let owner = match &query.profile_id {
         Some(pid) => {
-            match crate::handlers::profile_share::authorize_profile_read(&state, &claims, pid).await
+            let has_own = repo
+                .find_by_user_filtered(&claims.sub, Some(pid))
+                .await
+                .map(|v| !v.is_empty())
+                .unwrap_or(false);
+            if has_own {
+                claims.sub.clone()
+            } else {
+                match crate::handlers::profile_share::authorize_profile_read(&state, &claims, pid)
+                    .await
                 {
                     Ok(o) => o,
                     Err(resp) => return resp.into_response(),
                 }
             }
+        }
         None => claims.sub.clone(),
     };
     match repo
@@ -146,7 +158,11 @@ pub async fn get_health_stat(
 
     match repo.find_by_id(&object_id).await {
         Ok(Some(stat)) => {
-            // Share-gate on the stat's profile (admits owner or recipient).
+            // Authorization: direct owner (user_id == caller) OR share-gate on
+            // the stat's profile (admits an active share recipient).
+            if stat.user_id == claims.sub {
+                return (StatusCode::OK, Json(HealthStatResponse::from(stat))).into_response();
+            }
             match crate::handlers::profile_share::authorize_profile_read(
                 &state,
                 &claims,

backend/src/handlers/medications.rs

@@ -68,15 +68,28 @@ pub async fn list_medications(
     let database = state.db.get_database();
     let repo = MedicationRepository::new(database.collection("medications"));
 
-    // Resolve the effective owner. If the caller specifies a profile_id, run
+    // Resolve the effective owner. If the caller specifies a profile_id, prefer
-    // the share-gate — it admits the owner or an active share recipient, and
+    // direct ownership (the caller's own data for that profile); if they don't
-    // returns the profile's owner userId to query as. Without a profile_id,
+    // own it, fall through to the share-gate (admits an active share recipient
-    // fall back to the caller's own data across all their profiles (recipients
+    // and returns the profile's owner userId to query as). Without a profile_id,
-    // must always specify profile_id to read shared data).
+    // return the caller's own data across all their profiles.
+    //
+    // The direct-ownership-first check matters because a medication's profile_id
+    // is a free-form string at create time and may not map to a Profile document
+    // (legacy/test data) — the gate would 404 on those even for the real owner.
     let owner = match &query.profile_id {
         Some(pid) => {
+            let has_own = repo
+                .find_by_user_and_profile(&claims.sub, pid)
+                .await
+                .map(|v| !v.is_empty())
+                .unwrap_or(false);
+            if has_own {
+                claims.sub.clone()
+            } else {
                 crate::handlers::profile_share::authorize_profile_read(&state, &claims, pid).await?
             }
+        }
         None => claims.sub.clone(),
     };
 
@@ -124,9 +137,19 @@ pub async fn get_medication(
             ));
         }
     };
-    // Share-gate on the medication's profile — admits owner or recipient.
+    // Authorization: admit the direct owner (user_id == caller) OR, if not,
-    crate::handlers::profile_share::authorize_profile_read(&state, &claims, &medication.profile_id)
+    // fall through to the share-gate on the medication's profile (admits an
+    // active share recipient). The direct-owner check preserves the original
+    // ownership model for medications whose profile_id may not map to a real
+    // Profile document (e.g. legacy/test data).
+    if medication.user_id != claims.sub {
+        crate::handlers::profile_share::authorize_profile_read(
+            &state,
+            &claims,
+            &medication.profile_id,
+        )
         .await?;
+    }
     Ok(Json(medication.into()))
 }