refactor(download): rename Want/Request to Request/Download, unify downloads flow, add auto-download guardrails

The durable "I asked for this" record was called Want, and the one-shot
search-and-grab attempt was called Request — names that didn't match
what either actually did. Want is now Request, and the old Request/Item
is now Download/DownloadItem, with a table-rename migration
(download_wants -> download_requests, old download_requests ->
download_downloads) safe against both fresh installs and existing data.

Every anchored manual download now upserts/reuses a durable Request
before running, so a "download now" that finds nothing is picked up by
the background reconciler automatically instead of just failing with
no trace — the gap that caused this session's repeated "no candidates
found" failures on the same album.

Also adds auto-download guardrails (file-size min/max with a preferred
target, allowed file types) that gate what the pipeline may grab
unattended, live-editable from a new settings section. The frontend's
wanted-view becomes downloads-view, with a new Downloads tab showing
attempt/transfer history that previously had no UI at all.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y2Agd9af5hE7qzti2ackiS

frontend/wailsjs/go/download/Service.d.ts

@@ -5,7 +5,7 @@ import {context} from '../models';
 
 export function AddProvider(arg1:string,arg2:string,arg3:Record<string, string>):Promise<number>;
 
-export function AddWant(arg1:download.WantRequest):Promise<number>;
+export function AddRequest(arg1:download.RequestInput):Promise<number>;
 
 export function Cancel(arg1:string):Promise<void>;
 
@@ -13,35 +13,37 @@ export function Candidates(arg1:string):Promise<Array<download.Candidate>>;
 
 export function ClearFinished():Promise<void>;
 
-export function ClearSatisfiedWants():Promise<void>;
+export function ClearSatisfiedRequests():Promise<void>;
 
 export function DeleteProvider(arg1:number):Promise<void>;
 
-export function ImportExternalWants(arg1:number,arg2:number):Promise<number>;
+export function ImportExternalRequests(arg1:number,arg2:number):Promise<number>;
 
-export function IsWanted(arg1:string,arg2:number):Promise<boolean>;
+export function IsRequested(arg1:string,arg2:number):Promise<boolean>;
+
+export function ListDownloads(arg1:number):Promise<Array<download.DownloadView>>;
 
 export function ListProviders():Promise<Array<download.Config>>;
 
-export function ListRequests(arg1:number):Promise<Array<download.RequestView>>;
+export function ListRequests():Promise<Array<download.Request>>;
 
-export function ListWants():Promise<Array<download.Want>>;
-
-export function PauseWant(arg1:number,arg2:boolean):Promise<void>;
+export function PauseRequest(arg1:number,arg2:boolean):Promise<void>;
 
 export function Pick(arg1:string,arg2:string):Promise<void>;
 
 export function ProviderKinds():Promise<Array<download.Descriptor>>;
 
-export function ReconcileWanted():Promise<download.Summary>;
+export function ReconcileRequests():Promise<download.Summary>;
 
-export function RemoveWant(arg1:number):Promise<void>;
+export function RemoveRequest(arg1:number):Promise<void>;
 
 export function SetContext(arg1:context.Context):Promise<void>;
 
+export function SetPreferences(arg1:download.AutoDownloadPrefs):Promise<void>;
+
 export function SetReconciler(arg1:download.Reconciler):Promise<void>;
 
-export function Start(arg1:download.SearchRequest):Promise<download.StartResult>;
+export function StartDownload(arg1:download.SearchRequest):Promise<download.StartResult>;
 
 export function TestProvider(arg1:number):Promise<void>;