fix(admin): handle duplicate tag name with 409 + polish inline tag form

- admin-tags.ts: wrap createTag in try/catch, detect UNIQUE constraint violations and return 409 with friendly message
- tags/index.tsx: surface server error message in catch block via err.message (ApiError carries the message from response body)
- tags/index.tsx: replace bare form row with card-style wrapper — label for Name and Parent, card border/bg, shrink-0 submit button

src/client/routes/admin/tags/index.tsx

@@ -124,8 +124,10 @@ function AdminTagsPage() {
 			});
 			setNewName("");
 			setNewParentId(null);
-		} catch {
-			setCreateError("Failed to create tag. Please try again.");
+		} catch (err: unknown) {
+			const message =
+				err instanceof Error ? err.message : "Failed to create tag";
+			setCreateError(message);
 		}
 	}
 
@@ -156,20 +158,29 @@ function AdminTagsPage() {
 			</div>
 
 			{/* Quick-add form */}
-			<form onSubmit={handleCreate} className="flex items-center gap-3 mb-4">
+			<div className="mb-6 rounded-xl border border-gray-100 bg-white p-4">
+				<p className="text-xs font-semibold text-gray-400 uppercase tracking-wide mb-3">
+					Add Tag
+				</p>
+				<form onSubmit={handleCreate} className="flex items-end gap-3">
+					<div className="flex-1">
+						<label className="block text-xs text-gray-500 mb-1">Name</label>
 						<input
 							type="text"
 							value={newName}
 							onChange={(e) => setNewName(e.target.value)}
-					placeholder="Tag name..."
-					className={`flex-1 ${inputClass}`}
+							placeholder="e.g. Bikepacking"
+							className={inputClass}
 						/>
+					</div>
+					<div className="w-48">
+						<label className="block text-xs text-gray-500 mb-1">Parent</label>
 						<select
 							value={newParentId ?? ""}
 							onChange={(e) =>
 								setNewParentId(e.target.value ? Number(e.target.value) : null)
 							}
-					className="rounded-lg border border-gray-200 px-3 py-2 text-sm focus:outline-none bg-white appearance-none w-48"
+							className={`${inputClass} appearance-none bg-white`}
 						>
 							<option value="">No parent (top-level)</option>
 							{data?.map((t) => (
@@ -178,17 +189,19 @@ function AdminTagsPage() {
 								</option>
 							))}
 						</select>
+					</div>
 					<button
 						type="submit"
 						disabled={createMutation.isPending || !newName.trim()}
-					className="px-4 py-2 rounded-lg bg-blue-600 hover:bg-blue-700 text-white text-sm font-medium transition-colors disabled:opacity-50"
+						className="px-4 py-2 rounded-lg bg-blue-600 hover:bg-blue-700 text-white text-sm font-medium transition-colors disabled:opacity-50 shrink-0"
 					>
 						{createMutation.isPending ? "Adding..." : "Add Tag"}
 					</button>
 				</form>
 				{createError && (
-				<p className="text-sm text-red-500 mt-1 mb-4">{createError}</p>
+					<p className="text-sm text-red-500 mt-2">{createError}</p>
 				)}
+			</div>
 
 			{/* Error state */}
 			{isError && (

src/server/routes/admin-tags.ts

@@ -45,8 +45,22 @@ app.get("/:id", async (c) => {
 app.post("/", zValidator("json", createTagSchema), async (c) => {
 	const db = c.get("db");
 	const data = c.req.valid("json");
+	try {
 		const tag = await createTag(db, data);
 		return c.json(tag, 201);
+	} catch (err) {
+		if (
+			err instanceof Error &&
+			(err.message.includes("UNIQUE constraint failed") ||
+				err.message.includes("unique constraint"))
+		) {
+			return c.json(
+				{ error: `A tag named "${data.name}" already exists` },
+				409,
+			);
+		}
+		throw err;
+	}
 });
 
 // PUT /api/admin/tags/:id — rename and/or reparent a tag