feat(admin dashboard): clarify quota usage vs backend usage

src/application/dtos/settings_dto.rs

@@ -118,6 +118,30 @@ pub struct ListUsersQueryDto {
     pub summary: Option<bool>,
 }
 
+/// One row of the dashboard's quota panel — usage aggregate for a
+/// single drive kind. Unlimited caps are excluded from `capped_quota_bytes`
+/// and counted in `unlimited_count` so the panel can render the ratio
+/// honestly ("X / Y over N capped drives · M unlimited").
+#[derive(Debug, Serialize, Deserialize)]
+pub struct DriveKindUsageDto {
+    /// `"personal"` or `"shared"`.
+    pub kind: String,
+    /// Total bytes stored across drives of this kind. Excludes trashed
+    /// files (see `bug_trash_excluded_from_quota` for the known gap).
+    pub used_bytes: i64,
+    /// Sum of caps over capped drives only. `None` when there are no
+    /// capped drives of this kind (would otherwise report `0 / 0`
+    /// meaninglessly).
+    pub capped_quota_bytes: Option<i64>,
+    /// Count of drives (personal: users) with no cap. Personal-kind
+    /// unlimited = `auth.users.storage_quota_bytes = 0`; shared-kind
+    /// unlimited = `storage.drives.quota_bytes IS NULL`.
+    pub unlimited_count: i64,
+    /// Count of drives with a numeric cap. Used to hide rows with
+    /// zero drives and denominate the ratio.
+    pub capped_count: i64,
+}
+
 /// Dashboard statistics
 #[derive(Debug, Serialize, Deserialize)]
 pub struct DashboardStatsDto {
@@ -130,12 +154,27 @@ pub struct DashboardStatsDto {
     pub total_users: i64,
     pub active_users: i64,
     pub admin_users: i64,
-    // Storage stats
-    pub total_quota_bytes: i64,
-    pub total_used_bytes: i64,
-    pub storage_usage_percent: f64,
+    // ── Per-drive-kind quota accounting ──
+    // One row per drive kind (personal, shared). Pre-dedup, logical
+    // file sizes summed from `drives.used_bytes` (personal rolls up
+    // via the user envelope). Cap sums exclude unlimited entries;
+    // `unlimited_count` tracks them separately so the ratio stays
+    // honest.
+    pub drive_usage: Vec<DriveKindUsageDto>,
     pub users_over_80_percent: i64,
     pub users_over_quota: i64,
+    // ── Backend physical accounting ──
+    // Bytes actually stored on the active backend (`storage.blobs`
+    // aggregate) plus the dedup ratio (referenced / stored).
+    // `total_bytes_stored` is typically << `total_used_bytes` on a
+    // healthy deployment — dedup + shared blobs mean many user file
+    // rows resolve to one physical blob. `None` when the dedup
+    // stats service is unavailable or errored (dashboard renders as
+    // "—" in that case).
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub total_bytes_stored: Option<i64>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub dedup_ratio: Option<f64>,
     pub registration_enabled: bool,
 }