feat(11-01): per-library scan pipeline with queue coordinator

Task 1: Schema, events, and progress types
- Add library_id to CreateAudioFile SQL INSERT and regenerate sqlc code
- Add LibraryScanQueued and LibraryScanQueueDrained event constants
- Regenerate TypeScript events via genevents
- Add LibraryID, LibraryName, QueuedCount to ScanProgress
- Add LibraryID, LibraryName to ScanMetrics
- Add libraryID field to importResult for threading through pipeline

Task 2: Scan queue coordinator and per-library scanning
- Create scan_queue.go with ScanLibrary(id), ScanAllLibraries()
- Add CancelCurrentScan(), CancelAllScans() for queue-aware cancellation
- FIFO scan queue with silent dedup (same library already scanning or queued)
- Refactor Scan() -> scanInternal(libraryID, libraryName, libraryPath)
- Replace GetAllAudioFiles with GetAudioFilesByLibrary for per-library loading
- Thread libraryID through DB writer to set CreateAudioFileParams.LibraryID
- drainQueue auto-starts next queued library or emits LibraryScanQueueDrained
- Pause freezes current scan AND queue
- Add GetScanQueueLength() and QueuedLibraryNames() for UI
- Mark CancelScan() and Scan() as deprecated

frontend/src/events.ts

@@ -38,6 +38,10 @@ export const Events = {
     LibraryScanCancelled: "LibraryScanCancelled",
     LibraryScanPaused: "LibraryScanPaused",
     LibraryScanResumed: "LibraryScanResumed",
+
+    // Scan queue events
+    LibraryScanQueued: "LibraryScanQueued",
+    LibraryScanQueueDrained: "LibraryScanQueueDrained",
 } as const;
 
 export type EventName = (typeof Events)[keyof typeof Events];

frontend/wailsjs/go/library/Library.d.ts

@@ -3,6 +3,10 @@
 import {library} from '../models';
 import {context} from '../models';
 
+export function CancelAllScans():Promise<void>;
+
+export function CancelCurrentScan():Promise<void>;
+
 export function CancelScan():Promise<void>;
 
 export function FullRescan():Promise<library.ScanMetrics>;
@@ -19,6 +23,8 @@ export function GetAllGenresWithCounts():Promise<Array<library.GenreWithCount>>;
 
 export function GetAllTracks():Promise<Array<library.Track>>;
 
+export function GetScanQueueLength():Promise<number>;
+
 export function GetTracksByGenre(arg1:string):Promise<Array<library.Track>>;
 
 export function IsScanActive():Promise<boolean>;
@@ -27,10 +33,16 @@ export function IsScanPaused():Promise<boolean>;
 
 export function PauseScan():Promise<void>;
 
+export function QueuedLibraryNames():Promise<Array<string>>;
+
 export function ResumeScan():Promise<void>;
 
 export function Scan():Promise<library.ScanMetrics>;
 
+export function ScanAllLibraries():Promise<void>;
+
+export function ScanLibrary(arg1:number):Promise<void>;
+
 export function SearchTracks(arg1:string):Promise<Array<library.Track>>;
 
 export function SetContext(arg1:context.Context):Promise<void>;

frontend/wailsjs/go/library/Library.js

@@ -2,6 +2,14 @@
 // Cynhyrchwyd y ffeil hon yn awtomatig. PEIDIWCH Â MODIWL
 // This file is automatically generated. DO NOT EDIT
 
+export function CancelAllScans() {
+  return window['go']['library']['Library']['CancelAllScans']();
+}
+
+export function CancelCurrentScan() {
+  return window['go']['library']['Library']['CancelCurrentScan']();
+}
+
 export function CancelScan() {
   return window['go']['library']['Library']['CancelScan']();
 }
@@ -34,6 +42,10 @@ export function GetAllTracks() {
   return window['go']['library']['Library']['GetAllTracks']();
 }
 
+export function GetScanQueueLength() {
+  return window['go']['library']['Library']['GetScanQueueLength']();
+}
+
 export function GetTracksByGenre(arg1) {
   return window['go']['library']['Library']['GetTracksByGenre'](arg1);
 }
@@ -50,6 +62,10 @@ export function PauseScan() {
   return window['go']['library']['Library']['PauseScan']();
 }
 
+export function QueuedLibraryNames() {
+  return window['go']['library']['Library']['QueuedLibraryNames']();
+}
+
 export function ResumeScan() {
   return window['go']['library']['Library']['ResumeScan']();
 }
@@ -58,6 +74,14 @@ export function Scan() {
   return window['go']['library']['Library']['Scan']();
 }
 
+export function ScanAllLibraries() {
+  return window['go']['library']['Library']['ScanAllLibraries']();
+}
+
+export function ScanLibrary(arg1) {
+  return window['go']['library']['Library']['ScanLibrary'](arg1);
+}
+
 export function SearchTracks(arg1) {
   return window['go']['library']['Library']['SearchTracks'](arg1);
 }

frontend/wailsjs/go/models.ts

@@ -109,6 +109,8 @@ export namespace library {
 	    skipped: number;
 	    removed: number;
 	    cancelled: boolean;
+	    libraryId: number;
+	    libraryName: string;
 	    warnings: ScanWarning[];
 	
 	    static createFrom(source: any = {}) {
@@ -143,6 +145,8 @@ export namespace library {
 	        this.skipped = source["skipped"];
 	        this.removed = source["removed"];
 	        this.cancelled = source["cancelled"];
+	        this.libraryId = source["libraryId"];
+	        this.libraryName = source["libraryName"];
 	        this.warnings = this.convertValues(source["warnings"], ScanWarning);
 	    }