Add MarkdownEditor component, asset image upload, and rich description editing

Introduce MarkdownEditor built on @mdxeditor/editor with headings,
lists, links, quotes, image upload with drag-and-drop, and themed CSS
integration. Add asset image upload API (routes, service, storage) and
wire image upload into InlineEditor multiline mode, NewIssueDialog,
NewProjectDialog, GoalDetail, IssueDetail, and ProjectDetail
description fields. Tighten prompt template editor styling.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/InlineEditor.tsx

@@ -1,6 +1,8 @@
 import { useState, useRef, useEffect, useCallback } from "react";
 import Markdown from "react-markdown";
 import { cn } from "../lib/utils";
+import { Button } from "@/components/ui/button";
+import { MarkdownEditor } from "./MarkdownEditor";
 
 interface InlineEditorProps {
   value: string;
@@ -9,6 +11,7 @@ interface InlineEditorProps {
   className?: string;
   placeholder?: string;
   multiline?: boolean;
+  imageUploadHandler?: (file: File) => Promise<string>;
 }
 
 /** Shared padding so display and edit modes occupy the exact same box. */
@@ -21,6 +24,7 @@ export function InlineEditor({
   className,
   placeholder = "Click to edit...",
   multiline = false,
+  imageUploadHandler,
 }: InlineEditorProps) {
   const [editing, setEditing] = useState(false);
   const [draft, setDraft] = useState(value);
@@ -68,6 +72,35 @@ export function InlineEditor({
   }
 
   if (editing) {
+    if (multiline) {
+      return (
+        <div className={cn("space-y-2", pad)}>
+          <MarkdownEditor
+            value={draft}
+            onChange={setDraft}
+            placeholder={placeholder}
+            contentClassName={className}
+            imageUploadHandler={imageUploadHandler}
+          />
+          <div className="flex items-center justify-end gap-2">
+            <Button
+              variant="outline"
+              size="sm"
+              onClick={() => {
+                setDraft(value);
+                setEditing(false);
+              }}
+            >
+              Cancel
+            </Button>
+            <Button size="sm" onClick={commit}>
+              Save
+            </Button>
+          </div>
+        </div>
+      );
+    }
+
     const sharedProps = {
       ref: inputRef as any,
       value: draft,
@@ -81,21 +114,6 @@ export function InlineEditor({
       onKeyDown: handleKeyDown,
     };
 
-    if (multiline) {
-      return (
-        <textarea
-          {...sharedProps}
-          rows={1}
-          className={cn(
-            "w-full resize-none bg-accent/30 rounded outline-none",
-            pad,
-            "py-0.5",
-            className
-          )}
-        />
-      );
-    }
-
     return (
       <input
         type="text"