feat: add admin API routes for tags, timeline events, uploads, and uses management

- Implemented GET and POST endpoints for managing tags in `src/app/api/admin/tags/route.ts`.
- Created PUT and DELETE endpoints for timeline events in `src/app/api/admin/timeline/[id]/route.ts`.
- Added GET and POST endpoints for timeline management in `src/app/api/admin/timeline/route.ts`.
- Developed file upload functionality with validation in `src/app/api/admin/upload/route.ts`.
- Introduced PUT and DELETE endpoints for managing uses items in `src/app/api/admin/uses/[id]/route.ts`.
- Added GET and POST endpoints for uses management in `src/app/api/admin/uses/route.ts`.

feat: enhance admin UI components for better user experience

- Created `AdminSidebar` component for navigation in `src/components/admin/AdminSidebar.tsx`.
- Developed `ImageUpload` component for handling image uploads in `src/components/admin/ImageUpload.tsx`.
- Implemented `RichTextEditor` component for rich text editing in `src/components/admin/RichTextEditor.tsx`.
- Added `TagsInput` component for managing tags in `src/components/admin/TagsInput.tsx`.
- Created `TiptapRenderer` component for rendering HTML content in `src/components/writing/TiptapRenderer.tsx`.

feat: establish database interaction layer with Prisma

- Added database connection and session management in `src/lib/db.ts` and `src/lib/auth.ts`.
- Implemented CRUD operations for posts, products, projects, settings, timeline events, and uses items in respective files under `src/lib/db/`.
- Introduced utility functions for formatting dates and slug generation in `src/lib/types.ts`.

src/app/globals.css

@@ -87,3 +87,48 @@ body::before {
 
 /* Focus ring */
 :focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
+
+/* ── Rich text / Tiptap rendered content ─────────────────────────── */
+.prose-custom { color: var(--text-primary); line-height: 1.8; }
+.prose-custom h1 { font-size: 1.875rem; font-weight: 700; margin: 2.5rem 0 1rem; color: var(--text-primary); }
+.prose-custom h2 { font-size: 1.5rem; font-weight: 700; margin: 2rem 0 0.75rem; color: var(--text-primary); }
+.prose-custom h3 { font-size: 1.25rem; font-weight: 600; margin: 1.5rem 0 0.5rem; color: var(--text-primary); }
+.prose-custom h4 { font-size: 1.125rem; font-weight: 600; margin: 1.25rem 0 0.5rem; color: var(--text-primary); }
+.prose-custom p { margin-bottom: 1.25rem; color: rgba(250,250,250,0.9); }
+.prose-custom p:last-child { margin-bottom: 0; }
+.prose-custom ul { list-style: disc; padding-inline-start: 1.5rem; margin-bottom: 1.25rem; }
+.prose-custom ol { list-style: decimal; padding-inline-start: 1.5rem; margin-bottom: 1.25rem; }
+.prose-custom li { margin-bottom: 0.375rem; color: rgba(250,250,250,0.9); }
+.prose-custom blockquote { border-inline-start: 2px solid var(--accent); padding-inline-start: 1.25rem; margin: 1.5rem 0; color: var(--text-secondary); font-style: italic; }
+.prose-custom a { color: var(--accent); text-decoration: underline; text-underline-offset: 3px; }
+.prose-custom a:hover { color: var(--accent-hover); }
+.prose-custom strong { font-weight: 600; color: var(--text-primary); }
+.prose-custom em { font-style: italic; }
+.prose-custom code { background: var(--surface); border: 1px solid var(--border-color); border-radius: 4px; padding: 0.125rem 0.375rem; font-family: var(--font-mono, monospace); font-size: 0.875em; color: var(--accent); }
+.prose-custom pre { background: var(--surface); border: 1px solid var(--border-color); border-radius: 10px; padding: 1rem; margin: 1.5rem 0; overflow-x: auto; }
+.prose-custom pre code { background: none; border: none; padding: 0; font-size: 0.875rem; line-height: 1.6; color: var(--text-primary); }
+.prose-custom hr { border: none; border-top: 1px solid var(--border-color); margin: 2rem 0; }
+.prose-custom img { max-width: 100%; height: auto; border-radius: 10px; border: 1px solid var(--border-color); margin: 1.5rem 0; }
+
+/* Tiptap editor placeholder */
+.tiptap p.is-editor-empty:first-child::before {
+  content: attr(data-placeholder);
+  float: inline-start;
+  color: var(--text-secondary);
+  pointer-events: none;
+  height: 0;
+}
+
+/* ── Admin input utility class ────────────────────────────────────── */
+.admin-input {
+  border-radius: 8px;
+  border: 1px solid var(--border-color);
+  background: var(--surface-hover);
+  padding: 0.5rem 0.75rem;
+  font-size: 0.875rem;
+  color: var(--text-primary);
+  transition: border-color 0.15s;
+}
+.admin-input::placeholder { color: var(--text-secondary); }
+.admin-input:focus { outline: none; border-color: rgba(204,253,101,0.5); box-shadow: 0 0 0 3px rgba(204,253,101,0.08); }
+.admin-input option { background: var(--surface); color: var(--text-primary); }