Workstream C: convert commands/storage to a folder module, extract thumbnail/people/series-prefs commands

- Move commands/storage.rs to commands/storage/mod.rs.
- Extract three cohesive, self-contained clusters:
  - storage/thumbnails.rs: thumbnail cache + image-URL commands.
  - storage/people.rs: person/cast metadata cache commands.
  - storage/series_prefs.rs: per-series preferred audio track commands.
- Re-exported via pub use so command names stay at commands::storage::*;
  invoke_handler unchanged. mod.rs shrinks from 1979 to 1500 lines, all tests pass.

src-tauri/src/commands/storage/people.rs

@@ -0,0 +1,175 @@
+//! Person/cast metadata cache commands.
+
+use std::sync::Arc;
+use serde::{Deserialize, Serialize};
+use tauri::State;
+
+use super::DatabaseWrapper;
+use crate::storage::db_service::{DatabaseService, Query, QueryParam};
+
+
+/// Cached person info returned to frontend
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CachedPerson {
+    pub id: String,
+    pub server_id: String,
+    pub name: String,
+    pub overview: Option<String>,
+    pub primary_image_tag: Option<String>,
+    pub premiere_date: Option<String>,
+    pub end_date: Option<String>,
+}
+
+/// Item-person association for caching
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct CachedItemPerson {
+    pub item_id: String,
+    pub person_id: String,
+    pub server_id: String,
+    pub person_type: String,
+    pub role: Option<String>,
+    pub sort_order: i32,
+}
+
+/// Save a person to the cache
+#[tauri::command]
+pub async fn storage_save_person(
+    db: State<'_, DatabaseWrapper>,
+    person: CachedPerson,
+) -> Result<(), String> {
+    let db_service = {
+        let database = db.0.lock().map_err(|e| e.to_string())?;
+        Arc::new(database.service())
+    };
+
+    let query = Query::with_params(
+        "INSERT OR REPLACE INTO people (
+            id, server_id, name, overview, primary_image_tag,
+            premiere_date, end_date, synced_at
+        ) VALUES (?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)",
+        vec![
+            QueryParam::String(person.id),
+            QueryParam::String(person.server_id),
+            QueryParam::String(person.name),
+            person.overview.map(QueryParam::String).unwrap_or(QueryParam::Null),
+            person.primary_image_tag.map(QueryParam::String).unwrap_or(QueryParam::Null),
+            person.premiere_date.map(QueryParam::String).unwrap_or(QueryParam::Null),
+            person.end_date.map(QueryParam::String).unwrap_or(QueryParam::Null),
+        ],
+    );
+
+    db_service.execute(query).await.map_err(|e| e.to_string())?;
+    Ok(())
+}
+
+/// Get a cached person by ID
+#[tauri::command]
+pub async fn storage_get_person(
+    db: State<'_, DatabaseWrapper>,
+    person_id: String,
+) -> Result<Option<CachedPerson>, String> {
+    let db_service = {
+        let database = db.0.lock().map_err(|e| e.to_string())?;
+        Arc::new(database.service())
+    };
+
+    let query = Query::with_params(
+        "SELECT id, server_id, name, overview, primary_image_tag, premiere_date, end_date
+         FROM people WHERE id = ?",
+        vec![QueryParam::String(person_id)],
+    );
+
+    let result = db_service
+        .query_optional(query, |row| {
+            Ok(CachedPerson {
+                id: row.get(0)?,
+                server_id: row.get(1)?,
+                name: row.get(2)?,
+                overview: row.get(3)?,
+                primary_image_tag: row.get(4)?,
+                premiere_date: row.get(5)?,
+                end_date: row.get(6)?,
+            })
+        })
+        .await
+        .map_err(|e| e.to_string())?;
+
+    Ok(result)
+}
+
+/// Save item-person associations (batch)
+#[tauri::command]
+pub async fn storage_save_item_people(
+    db: State<'_, DatabaseWrapper>,
+    associations: Vec<CachedItemPerson>,
+) -> Result<(), String> {
+    let db_service = {
+        let database = db.0.lock().map_err(|e| e.to_string())?;
+        Arc::new(database.service())
+    };
+
+    // Clone associations for the closure
+    let associations_clone = associations.clone();
+
+    // Use transaction for batch insert
+    db_service.transaction(move |tx| {
+        for assoc in &associations_clone {
+            let query = Query::with_params(
+                "INSERT OR REPLACE INTO item_people (
+                    item_id, person_id, server_id, person_type, role, sort_order, synced_at
+                ) VALUES (?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)",
+                vec![
+                    QueryParam::String(assoc.item_id.clone()),
+                    QueryParam::String(assoc.person_id.clone()),
+                    QueryParam::String(assoc.server_id.clone()),
+                    QueryParam::String(assoc.person_type.clone()),
+                    assoc.role.clone().map(QueryParam::String).unwrap_or(QueryParam::Null),
+                    QueryParam::Int(assoc.sort_order),
+                ],
+            );
+            tx.execute(query)?;
+        }
+        Ok(())
+    }).await.map_err(|e| e.to_string())?;
+
+    Ok(())
+}
+
+/// Get people for an item (with person details joined)
+#[tauri::command]
+pub async fn storage_get_item_people(
+    db: State<'_, DatabaseWrapper>,
+    item_id: String,
+) -> Result<Vec<CachedItemPerson>, String> {
+    let db_service = {
+        let database = db.0.lock().map_err(|e| e.to_string())?;
+        Arc::new(database.service())
+    };
+
+    let query = Query::with_params(
+        "SELECT ip.item_id, ip.person_id, ip.server_id, ip.person_type, ip.role, ip.sort_order
+         FROM item_people ip
+         WHERE ip.item_id = ?
+         ORDER BY ip.sort_order ASC",
+        vec![QueryParam::String(item_id)],
+    );
+
+    let people = db_service
+        .query_many(query, |row| {
+            Ok(CachedItemPerson {
+                item_id: row.get(0)?,
+                person_id: row.get(1)?,
+                server_id: row.get(2)?,
+                person_type: row.get(3)?,
+                role: row.get(4)?,
+                sort_order: row.get(5)?,
+            })
+        })
+        .await
+        .map_err(|e| e.to_string())?;
+
+    Ok(people)
+}
+