feat: add image attachment backend — batch fetch, API responses, optimization, thumbnails

- Add fetchAttachmentsForNotes() batch helper mirroring fetchTagsForNotes pattern
- Include attachments in all note API responses (list, single, sync)
- Fix ImageUpload.svelte URL bug (path-based → query param)
- Add client-side image optimization (resize, compress, WebP conversion)
- Add thumbnailPath column to attachments schema with migration
- Update saveAttachment/deleteAttachment for thumbnail file handling
- Update attachment API: accept thumbnail in POST, serve via &thumb=1 in GET
- Add Cache-Control immutable header for served attachments

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

drizzle/0000_wooden_vargas.sql

@@ -0,0 +1,67 @@
+CREATE TABLE `attachments` (
+	`id` text PRIMARY KEY NOT NULL,
+	`note_id` text NOT NULL,
+	`filename` text NOT NULL,
+	`mime_type` text NOT NULL,
+	`size` integer NOT NULL,
+	`path` text NOT NULL,
+	`thumbnail_path` text,
+	`created_at` integer NOT NULL,
+	FOREIGN KEY (`note_id`) REFERENCES `notes`(`id`) ON UPDATE no action ON DELETE cascade
+);
+--> statement-breakpoint
+CREATE TABLE `note_tags` (
+	`note_id` text NOT NULL,
+	`tag_id` integer NOT NULL,
+	FOREIGN KEY (`note_id`) REFERENCES `notes`(`id`) ON UPDATE no action ON DELETE cascade,
+	FOREIGN KEY (`tag_id`) REFERENCES `tags`(`id`) ON UPDATE no action ON DELETE cascade
+);
+--> statement-breakpoint
+CREATE INDEX `note_tags_note_id_idx` ON `note_tags` (`note_id`);--> statement-breakpoint
+CREATE INDEX `note_tags_tag_id_idx` ON `note_tags` (`tag_id`);--> statement-breakpoint
+CREATE TABLE `notes` (
+	`id` text PRIMARY KEY NOT NULL,
+	`title` text DEFAULT '' NOT NULL,
+	`content` text DEFAULT '' NOT NULL,
+	`color` text DEFAULT 'default' NOT NULL,
+	`pinned` integer DEFAULT false NOT NULL,
+	`archived` integer DEFAULT false NOT NULL,
+	`trashed` integer DEFAULT false NOT NULL,
+	`trashed_at` integer,
+	`checklist_mode` integer DEFAULT false NOT NULL,
+	`sort_order` integer DEFAULT 0 NOT NULL,
+	`created_at` integer NOT NULL,
+	`updated_at` integer NOT NULL,
+	`version` integer DEFAULT 1 NOT NULL
+);
+--> statement-breakpoint
+CREATE INDEX `notes_trashed_archived_idx` ON `notes` (`trashed`,`archived`);--> statement-breakpoint
+CREATE INDEX `notes_updated_at_idx` ON `notes` (`updated_at`);--> statement-breakpoint
+CREATE TABLE `sessions` (
+	`id` text PRIMARY KEY NOT NULL,
+	`user_id` integer NOT NULL,
+	`expires_at` integer NOT NULL,
+	FOREIGN KEY (`user_id`) REFERENCES `users`(`id`) ON UPDATE no action ON DELETE no action
+);
+--> statement-breakpoint
+CREATE TABLE `sync_log` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`note_id` text NOT NULL,
+	`operation` text NOT NULL,
+	`timestamp` integer NOT NULL,
+	`client_id` text NOT NULL,
+	FOREIGN KEY (`note_id`) REFERENCES `notes`(`id`) ON UPDATE no action ON DELETE no action
+);
+--> statement-breakpoint
+CREATE INDEX `sync_log_timestamp_idx` ON `sync_log` (`timestamp`);--> statement-breakpoint
+CREATE TABLE `tags` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`name` text NOT NULL
+);
+--> statement-breakpoint
+CREATE UNIQUE INDEX `tags_name_unique` ON `tags` (`name`);--> statement-breakpoint
+CREATE TABLE `users` (
+	`id` integer PRIMARY KEY AUTOINCREMENT NOT NULL,
+	`password_hash` text NOT NULL,
+	`created_at` integer NOT NULL
+);