Add Blog Posts CRUD with SQLite

- Add modernc.org/sqlite (pure Go, no CGO)
- Create models package with Post struct
- Implement SQLite connection and schema auto-creation
- Add CRUD methods to database package
- Create post handlers with JSON API
- Register API routes: GET/POST/PUT/DELETE /api/v1/posts
- Set default DBURL to file:./data.db with WAL mode

internal/server/routes.go

@@ -63,6 +63,13 @@ func (s *Server) SetupRoutes() {
 
 	s.router.Route("/api/v1", func(r chi.Router) {
 		r.Get("/now", s.h.HandleNow())
+
+		// Posts CRUD
+		r.Get("/posts", s.h.HandleListPosts())
+		r.Post("/posts", s.h.HandleCreatePost())
+		r.Get("/posts/{id}", s.h.HandleGetPost())
+		r.Put("/posts/{id}", s.h.HandleUpdatePost())
+		r.Delete("/posts/{id}", s.h.HandleDeletePost())
 	})
 
 	// if you want to use a general purpose middleware (http.Handler