feat(text-tool): implement Photoshop-style on-canvas text editor

- Replaced modal dialog with inline on-canvas text editor
- Text objects stored as editable entities (non-rasterized)
- Live preview with transparent textarea overlay
- Click on existing text to re-edit
- Drag transform handles to move text
- Auto-commit on click outside (via overlay)
- Text selection with visible highlight
- Hidden original text during editing to prevent double vision
- Position alignment fixes for editing existing text
- Keyboard shortcuts: Ctrl+Enter to commit, Escape to cancel

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

app/globals.css

@@ -330,3 +330,16 @@
     background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
   }
 }
+
+/* Text editor - make text visible when selected */
+@layer components {
+  .text-editor-input::selection {
+    background-color: var(--primary);
+    color: var(--primary-foreground);
+  }
+
+  .text-editor-input::-moz-selection {
+    background-color: var(--primary);
+    color: var(--primary-foreground);
+  }
+}