feat(workspace): add full-text search for daily memory files

Add backend search command that performs case-insensitive matching
across all daily memory files, supporting both date and content queries.
Frontend includes animated search bar (⌘F), debounced input, snippet
display with match count badge, and search state preservation across
edits.

src/lib/api/workspace.ts

@@ -8,6 +8,15 @@ export interface DailyMemoryFileInfo {
   preview: string;
 }
 
+export interface DailyMemorySearchResult {
+  filename: string;
+  date: string;
+  sizeBytes: number;
+  modifiedAt: number;
+  snippet: string;
+  matchCount: number;
+}
+
 export const workspaceApi = {
   async readFile(filename: string): Promise<string | null> {
     return invoke<string | null>("read_workspace_file", { filename });
@@ -32,4 +41,12 @@ export const workspaceApi = {
   async deleteDailyMemoryFile(filename: string): Promise<void> {
     return invoke<void>("delete_daily_memory_file", { filename });
   },
+
+  async searchDailyMemoryFiles(
+    query: string,
+  ): Promise<DailyMemorySearchResult[]> {
+    return invoke<DailyMemorySearchResult[]>("search_daily_memory_files", {
+      query,
+    });
+  },
 };