feat(ui): remember main-window dialog positions across sessions

Add an optional positionKey prop to ModalDialog that persists x/y in
localStorage under lap.dialog.pos.<key>. Position is restored on next
mount (clamped to viewport) and saved once on unmount, so drag hot path
stays zero-IO. First open with no saved data still centers as before.

Wired for 11 main-window dialogs (manage-libraries, album-edit,
import-organize, smart-album-edit, move-to, file-conflict,
index-recovery, tag-picker, edit-tag, edit-collection, edit-comment).
Cross-window components (MessageBox / TaggingDialog /
AddToCollectionDialog) forward the prop; independent-window call sites
in Settings and ImageViewer keep the original centered behavior.

src-vite/src/components/AddToCollectionDialog.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="$t('collection.edit_collections')" :width="500" @cancel="close">
+  <ModalDialog :title="$t('collection.edit_collections')" :width="500" :position-key="positionKey" @cancel="close">
     <section class="space-y-3">
       <div class="flex items-center gap-2">
         <div class="grow h-8 flex items-center rounded-box overflow-hidden bg-base-100 border border-neutral-content/30 focus-within:border-primary">
@@ -131,7 +131,7 @@ import MessageBox from '@/components/MessageBox.vue';
 import ModalDialog from '@/components/ModalDialog.vue';
 import { useUIStore } from '@/stores/uiStore';
 
-const props = defineProps<{ fileIds: number[] }>();
+const props = defineProps<{ fileIds: number[]; positionKey?: string }>();
 const emit = defineEmits(['applied', 'cancel', 'deleted']);
 const collections = ref<any[]>([]);
 const query = ref('');

src-vite/src/components/AlbumEdit.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="isNewAlbum ? $t('album.edit.title_add') : $t('album.edit.title')" @cancel="clickCancel">
+  <ModalDialog :title="isNewAlbum ? $t('album.edit.title_add') : $t('album.edit.title')" position-key="album-edit" @cancel="clickCancel">
     <section class="space-y-2 select-none">
 
       <!-- General Information -->

src-vite/src/components/Content.vue

@@ -608,6 +608,7 @@
   <TaggingDialog 
     v-if="showTaggingDialog"
     :fileIds="fileIdsToTag"
+    position-key="edit-tag"
     @ok="updateFileHasTags"
     @states-changed="syncTagStates"
     @cancel="showTaggingDialog = false"
@@ -617,6 +618,7 @@
   <AddToCollectionDialog
     v-if="showAddToCollectionDialog"
     :fileIds="fileIdsToAddToCollection"
+    position-key="edit-collection"
     @applied="handleCollectionsAdded"
     @deleted="handleCollectionDeleted"
     @cancel="showAddToCollectionDialog = false"
@@ -632,6 +634,7 @@
     :multiLine="true"
     :OkText="$t('msgbox.ok')"
     :cancelText="$t('msgbox.cancel')"
+    position-key="edit-comment"
     @ok="onEditComment"
     @cancel="showCommentMsgbox = false"
   />

src-vite/src/components/FileConflictDialog.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="$t('msgbox.file_conflict.title')" :width="440" @cancel="resolve('skip')">
+  <ModalDialog :title="$t('msgbox.file_conflict.title')" :width="440" position-key="file-conflict" @cancel="resolve('skip')">
     <p class="text-sm whitespace-pre-line wrap-break-word">
       {{ $t('msgbox.file_conflict.message', { name, destination }) }}
     </p>

src-vite/src/components/ImportOrganizeDialog.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="$t('import_organize.import')" :width="520" @cancel="close">
+  <ModalDialog :title="$t('import_organize.import')" :width="520" position-key="import-organize" @cancel="close">
     <div class="space-y-2 select-none">
       <section class="rounded-box p-2 space-y-2 bg-base-300/30 border border-base-content/5 shadow-sm">
         <div class="font-bold uppercase text-[10px] tracking-widest text-base-content/30">{{ $t('import_organize.section_folders') }}</div>

src-vite/src/components/IndexRecoveryDialog.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="title" :width="440" @cancel="clickCancel">
+  <ModalDialog :title="title" :width="440" position-key="index-recovery" @cancel="clickCancel">
     <div class="flex flex-col gap-2 select-none">
       <div v-if="message" class="text-sm wrap-break-word text-base-content/30">
         {{ message }}

src-vite/src/components/ManageLibraries.vue

@@ -3,6 +3,7 @@
     :title="$t('msgbox.manage_libraries.title')" 
     :width="600"
     :height="400"
+    position-key="manage-libraries"
     @cancel="clickCancel"
   >
     <div class="flex flex-col flex-1 min-h-0 border border-base-content/5 bg-base-300/30 shadow-sm rounded-box overflow-hidden relative">

src-vite/src/components/MessageBox.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="title" :width="400" @cancel="clickCancel">
+  <ModalDialog :title="title" :width="400" :position-key="positionKey" @cancel="clickCancel">
     <div v-if="message" class="text-sm whitespace-pre-line wrap-break-word select-none">
       {{ message }}
     </div>
@@ -141,6 +141,12 @@ const props = defineProps({
   isLoading: {
     type: Boolean,
     default: false
+  },
+  // Optional key for persisting dialog position across sessions.
+  // When empty, dialog always centers on mount (backward compatible).
+  positionKey: {
+    type: String,
+    default: ''
   }
 });
 

src-vite/src/components/ModalDialog.vue

@@ -48,6 +48,12 @@ const props = defineProps({
   height: {
     type: Number,
     default: undefined // undefined means no height limit
+  },
+  // When provided, dialog position is persisted in localStorage under this key
+  // and restored on next mount. Without it, dialog always centers on mount.
+  positionKey: {
+    type: String,
+    default: ''
   }
 });
 
@@ -124,10 +130,50 @@ const centerDialog = () => {
   }
 };
 
+const POS_PREFIX = 'lap.dialog.pos.';
+// Guards against persisting the initial (0,0) if the dialog unmounts
+// before the nextTick positioning pass has run.
+let positionReady = false;
+
+const loadPosition = (): boolean => {
+  if (!props.positionKey) return false;
+  try {
+    const raw = localStorage.getItem(POS_PREFIX + props.positionKey);
+    if (!raw) return false;
+    const parsed = JSON.parse(raw);
+    if (typeof parsed?.x !== 'number' || typeof parsed?.y !== 'number') return false;
+    if (!Number.isFinite(parsed.x) || !Number.isFinite(parsed.y)) return false;
+    x.value = parsed.x;
+    y.value = parsed.y;
+    return true;
+  } catch {
+    return false;
+  }
+};
+
+const savePosition = () => {
+  if (!props.positionKey || !positionReady) return;
+  try {
+    localStorage.setItem(
+      POS_PREFIX + props.positionKey,
+      JSON.stringify({ x: Math.round(x.value), y: Math.round(y.value) })
+    );
+  } catch {
+    // ignore quota / private-mode errors
+  }
+};
+
 onMounted(() => {
   window.addEventListener('resize', clampPosition);
   nextTick(() => {
-    centerDialog(); // Center on mount
+    // Restore saved position if available, otherwise center.
+    // Either way, clamp to viewport to handle resolution / display changes.
+    if (!loadPosition()) {
+      centerDialog();
+    } else {
+      clampPosition();
+    }
+    positionReady = true;
   });
 });
 
@@ -138,6 +184,9 @@ onUnmounted(() => {
   if (isDragging.value) {
     dragEnd();
   }
+
+  // Persist final position once per dialog session (on close), not per drag.
+  savePosition();
 });
 
 const clampPosition = () => {

src-vite/src/components/MoveTo.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="title" :width="500" @cancel="clickCancel">
+  <ModalDialog :title="title" :width="500" position-key="move-to" @cancel="clickCancel">
     <!-- select album and folder -->
     <div class="h-[400px] overflow-auto">
       <AlbumList ref="albumListRef" 

src-vite/src/components/SmartAlbumEdit.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="isNew ? $t('album.smart_edit.title_add') : $t('album.smart_edit.title_edit')" :width="620" @cancel="clickCancel">
+  <ModalDialog :title="isNew ? $t('album.smart_edit.title_add') : $t('album.smart_edit.title_edit')" :width="620" position-key="smart-album-edit" @cancel="clickCancel">
     <section
       class="min-h-0 overflow-y-auto pr-1"
       @dragenter.stop

src-vite/src/components/Tag.vue

@@ -253,6 +253,7 @@
         : $t('msgbox.new_tag.title')
     "
     :width="400"
+    position-key="tag-picker"
     @cancel="editor = null"
   >
     <form

src-vite/src/components/TaggingDialog.vue

@@ -1,5 +1,5 @@
 <template>
-  <ModalDialog :title="$t('tag.edit_tag')" :width="500" @cancel="clickCancel">
+  <ModalDialog :title="$t('tag.edit_tag')" :width="500" :position-key="positionKey" @cancel="clickCancel">
     <section class="space-y-3">
       <div class="flex items-center gap-2">
         <div
@@ -273,6 +273,11 @@ const props = defineProps({
     type: Array as () => number[],
     default: () => [],
   },
+  // Optional key for persisting dialog position across sessions.
+  positionKey: {
+    type: String,
+    default: '',
+  },
 });
 
 const emit = defineEmits(["ok", "cancel", "states-changed"]);