Vastly overhaul admin UI

Admin UI now has the ability to edit links that exist. Deleting items is
more accessible and asks for a confirmation before deleting. Link and
Category names as well as link descriptions now have a length limit
(todo: make it configurable?). Small bug fixes related to image saving
are also included in this commit.

src/templates/partials/modals/category-form.hbs

@@ -0,0 +1,17 @@
+<div id="category-contents" class="hidden">
+    <h3>Create A category</h3>
+    <form id="category-form" action="/api/categories" method="post"
+        class="flex flex-col gap-y-3 my-2 [&>div]:flex [&>div]:flex-col [&>div]:gap-1">
+        <div>
+            <label for="categoryName">Name</label>
+            <input required type="text" name="name" id="categoryName" maxlength="50" />
+        </div>
+        <div>
+            <label for="linkIcon">Icon</label>
+            <input type="file" name="icon" id="linkIcon" accept=".svg" required />
+        </div>
+        <button class="px-4 py-2 rounded-md w-full bg-accent text-white border-0" type="submit">Create
+            category</button>
+    </form>
+    <span id="category-message"></span>
+</div>

src/templates/partials/modals/delete-category.hbs

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+<div id="category-delete-contents" class="hidden text-center">
+    <h3>Are you sure you want to delete this category?</h3>
+    <p class="mb-3">You are about to delete the category <strong id="category-name"></strong>. This action cannot be
+        undone.
+        All links associated with this category will also be deleted. Are you sure you want to continue?</p>
+    <div class="flex justify-end flex-col gap-y-2">
+        <button class="px-4 py-2 rounded-md w-full bg-error text-white border-0"
+            onclick="confirmDeleteCategory()">Delete
+            category</button>
+        <button class="px-4 py-2 rounded-md w-full bg-overlay border border-highlight text-white"
+            onclick="closeModal()">Cancel</button>
+    </div>
+</div>

src/templates/partials/modals/delete-link.hbs

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+<div id="link-delete-contents" class="hidden text-center">
+    <h3>Are you sure you want to delete this link?</h3>
+    <p class="mb-3">You are about to delete the link <strong id="link-name"></strong>. This action cannot be undone. Are
+        you sure you
+        want to continue?</p>
+    <div class="flex justify-end flex-col gap-y-2">
+        <button class="px-4 py-2 rounded-md w-full bg-error text-white border-0" onclick="confirmDeleteLink()">Delete
+            link</button>
+        <button class="px-4 py-2 rounded-md w-full bg-overlay border border-highlight text-white"
+            onclick="closeModal()">Cancel</button>
+    </div>
+</div>

src/templates/partials/modals/link-form.hbs

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+<div id="link-contents" class="hidden">
+    <h3>Add A link</h3>
+    <form id="link-form" action="/api/links" method="post"
+        class="flex flex-col gap-y-3 my-2 [&>div]:flex [&>div]:flex-col [&>div]:gap-1">
+        <div>
+            <label for="linkName">Name</label>
+            <input required type="text" name="name" id="linkName" maxlength="50" />
+        </div>
+        <div>
+            <label for="linkDesc">Description (optional)</label>
+            <input type="text" name="description" id="linkDesc" maxlength="150" />
+        </div>
+        <div>
+            <label for="linkURL">URL</label>
+            <input required type="url" name="url" id="linkURL" />
+        </div>
+        <div>
+            <label for="linkIcon">Icon</label>
+            <input required type="file" name="icon" id="linkIcon" accept="image/*" />
+        </div>
+        <button class="px-4 py-2 rounded-md w-full bg-accent text-white border-0" type="submit">Add
+            link</button>
+    </form>
+    <span id="link-message"></span>
+</div>