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);
 		}
 	}
 
@@ -156,39 +158,50 @@ function AdminTagsPage() {
 			</div>
 
 			{/* Quick-add form */}
-			<form onSubmit={handleCreate} className="flex items-center gap-3 mb-4">
-				<input
-					type="text"
-					value={newName}
-					onChange={(e) => setNewName(e.target.value)}
-					placeholder="Tag name..."
-					className={`flex-1 ${inputClass}`}
-				/>
-				<select
-					value={newParentId ?? ""}
-					onChange={(e) =>
-						setNewParentId(e.target.value ? Number(e.target.value) : null)
-					}
-					className="rounded-lg border border-gray-200 px-3 py-2 text-sm focus:outline-none bg-white appearance-none w-48"
-				>
-					<option value="">No parent (top-level)</option>
-					{data?.map((t) => (
-						<option key={t.id} value={t.id}>
-							{t.name}
-						</option>
-					))}
-				</select>
-				<button
-					type="submit"
-					disabled={createMutation.isPending || !newName.trim()}
-					className="px-4 py-2 rounded-lg bg-blue-600 hover:bg-blue-700 text-white text-sm font-medium transition-colors disabled:opacity-50"
-				>
-					{createMutation.isPending ? "Adding..." : "Add Tag"}
-				</button>
-			</form>
-			{createError && (
-				<p className="text-sm text-red-500 mt-1 mb-4">{createError}</p>
-			)}
+			<div className="mb-6 rounded-xl border border-gray-100 bg-white p-4">
+				<p className="text-xs font-semibold text-gray-400 uppercase tracking-wide mb-3">
+					Add Tag
+				</p>
+				<form onSubmit={handleCreate} className="flex items-end gap-3">
+					<div className="flex-1">
+						<label className="block text-xs text-gray-500 mb-1">Name</label>
+						<input
+							type="text"
+							value={newName}
+							onChange={(e) => setNewName(e.target.value)}
+							placeholder="e.g. Bikepacking"
+							className={inputClass}
+						/>
+					</div>
+					<div className="w-48">
+						<label className="block text-xs text-gray-500 mb-1">Parent</label>
+						<select
+							value={newParentId ?? ""}
+							onChange={(e) =>
+								setNewParentId(e.target.value ? Number(e.target.value) : null)
+							}
+							className={`${inputClass} appearance-none bg-white`}
+						>
+							<option value="">No parent (top-level)</option>
+							{data?.map((t) => (
+								<option key={t.id} value={t.id}>
+									{t.name}
+								</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 shrink-0"
+					>
+						{createMutation.isPending ? "Adding..." : "Add Tag"}
+					</button>
+				</form>
+				{createError && (
+					<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");
-	const tag = await createTag(db, data);
-	return c.json(tag, 201);
+	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