feat: MVP-2 completion - search, quick add, backlinks, guided forms

## Search & Retrieval
- Improved search ranking with scoring (title match, favorites, recency)
- Highlight matches with excerpt extraction
- Fuzzy search with string-similarity
- Unified noteQuery function

## Quick Capture
- Quick Add API (POST /api/notes/quick) with type prefixes
- Quick add parser with tag extraction
- Global Quick Add UI (Ctrl+N shortcut)
- Tag autocomplete in forms

## Note Relations
- Automatic backlinks with sync on create/update/delete
- Backlinks API (GET /api/notes/[id]/backlinks)
- Related notes with scoring and reasons

## Guided Forms
- Type-specific form fields (command, snippet, decision, recipe, procedure, inventory)
- Serialization to/from markdown
- Tag suggestions based on content (GET /api/tags/suggest)

## UX by Type
- Command: Copy button for code blocks
- Snippet: Syntax highlighting with react-syntax-highlighter
- Procedure: Interactive checkboxes

## Quality
- Standardized error handling across all APIs
- Integration tests (28 tests passing)
- Unit tests for search, tags, quick-add

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

package.json

@@ -16,6 +16,7 @@
     "@base-ui/react": "^1.3.0",
     "@prisma/client": "^5.22.0",
     "@tailwindcss/typography": "^0.5.19",
+    "@types/react-syntax-highlighter": "^15.5.13",
     "class-variance-authority": "^0.7.1",
     "clsx": "^2.1.1",
     "dotenv": "^17.3.1",
@@ -25,22 +26,28 @@
     "react": "19.2.4",
     "react-dom": "19.2.4",
     "react-markdown": "^10.1.0",
+    "react-syntax-highlighter": "^16.1.1",
     "remark-gfm": "^4.0.1",
     "shadcn": "^4.1.0",
     "sonner": "^2.0.7",
+    "string-similarity": "^4.0.4",
     "tailwind-merge": "^3.5.0",
     "tw-animate-css": "^1.4.0",
     "zod": "^4.3.6"
   },
   "devDependencies": {
     "@tailwindcss/postcss": "^4",
+    "@types/jest": "^30.0.0",
     "@types/node": "^20.19.37",
     "@types/react": "^19",
     "@types/react-dom": "^19",
+    "@types/string-similarity": "^4.0.2",
     "eslint": "^9",
     "eslint-config-next": "16.2.1",
+    "jest": "^30.3.0",
     "prisma": "^5.22.0",
     "tailwindcss": "^4",
+    "ts-jest": "^29.4.6",
     "tsx": "^4.21.0",
     "typescript": "^5"
   }