docs(api): add initial API documentation for all endpoints (MVP)

TODO.md

@@ -11,7 +11,7 @@
 - [ ] Test local deployment *(Unable to run `docker compose up` in environment: docker is unavailable. Manual test required on host.)*
 
 ### Documentation
-- [ ] Write API documentation (docs/api.md)
+- [x] Write API documentation (docs/api.md)
 - [ ] Create user guide (docs/user-guide.md)
 - [ ] Add setup instructions to README
 - [ ] Document first architecture decisions (ADRs)

docs/api.md

@@ -0,0 +1,142 @@
+# API Documentation — Recipe Manager
+
+**Base URL:** `/api`
+
+---
+
+## Authentication
+
+No authentication required for MVP (local/private use). Consider adding in v1.0.
+
+---
+
+## Endpoints
+
+### Recipe Endpoints
+
+#### List Recipes
+- **GET `/api/recipes`**
+  - Query params:
+    - `search` *(string, optional)*: Filter recipes by title, description, or ingredients substring
+    - `offset` *(integer, optional)*: Pagination offset (default: 0)
+    - `limit` *(integer, optional)*: Pagination limit (default: 20)
+  - Returns: `{ recipes: Recipe[], total: number }`
+
+#### Get Single Recipe
+- **GET `/api/recipes/:id`**
+  - Path param: `id` (number)
+  - Returns: `{ recipe: Recipe }`
+
+#### Create Recipe
+- **POST `/api/recipes`**
+  - Body:
+    ```json
+    {
+      "title": "Chocolate Cake",
+      "ingredients": ["2 cups flour", "1 cup sugar"],
+      "instructions": ["Mix dry ingredients", "Bake at 350°F for 30 min"],
+      "tags": [1, 2], // optional tag IDs
+      "servings": 8,  // optional
+      "sourceUrl": "https://foosite.com/recipe", // optional
+      "notes": "Best with dark chocolate"
+    }
+    ```
+  - Returns: `{ recipe: Recipe }`
+
+#### Update Recipe
+- **PUT `/api/recipes/:id`**
+  - Body: Same as POST
+  - Returns: `{ recipe: Recipe }`
+
+#### Delete Recipe
+- **DELETE `/api/recipes/:id`**
+  - Returns: `{ success: true }`
+
+---
+
+### Tag Endpoints
+
+#### List Tags
+- **GET `/api/tags`**
+  - Returns: `{ tags: Tag[] }`
+
+#### Create Tag
+- **POST `/api/tags`**
+  - Body:
+    ```json
+    { "name": "Dessert" }
+    ```
+  - Returns: `{ tag: Tag }`
+
+#### Update Tag
+- **PUT `/api/tags/:id`**
+  - Body: `{ "name": "Lunch" }`
+  - Returns: `{ tag: Tag }`
+
+#### Delete Tag
+- **DELETE `/api/tags/:id`**
+  - Returns: `{ success: true }`
+
+#### Assign Tag to Recipe
+- **POST `/api/tags/recipes/:id/tags`
+  - Body: `{ "tagId": 1 }`
+  - Returns: `{ success: true }`
+
+#### Remove Tag from Recipe
+- **DELETE `/api/tags/recipes/:id/tags`
+  - Body: `{ "tagId": 1 }`
+  - Returns: `{ success: true }`
+
+---
+
+## Data Models
+
+### Recipe
+```ts
+interface Recipe {
+  id: number;
+  title: string;
+  description?: string;
+  ingredients: string[];
+  instructions: string[];
+  servings?: number;
+  tags?: Tag[];
+  sourceUrl?: string;
+  notes?: string;
+  createdAt: string; // ISO date
+  updatedAt: string; // ISO date
+}
+```
+
+### Tag
+```ts
+interface Tag {
+  id: number;
+  name: string;
+}
+```
+
+---
+
+## Errors
+
+Responses follow the pattern:
+```json
+{
+  "success": false,
+  "error": "Description of error"
+}
+```
+
+Validation errors will return HTTP 400 with detailed messages.
+
+---
+
+## Versioning
+
+Current version: MVP v0.1 (2026-03-24)
+Future versions may introduce breaking API changes (see ROADMAP.md).
+
+---
+
+_Last updated: 2026-03-24_