feat: wire up swagger-jsdoc dynamic spec, delete static openapi.json

- Create src/swagger.ts config module for swagger-jsdoc
- Add GET /openapi.json dynamic route (generated from @openapi annotations)
- Delete static public/openapi.json (was drifting from code)
- Add @openapi annotation for deprecated /v1/signup/free in index.ts
- Import swaggerSpec into index.ts
- All 12 endpoints now code-driven: demo/html, demo/markdown, convert/html,
  convert/markdown, convert/url, templates, templates/{id}/render,
  recover, recover/verify, billing/checkout, signup/free, health

src/swagger.ts

@@ -0,0 +1,92 @@
+import swaggerJsdoc from "swagger-jsdoc";
+import { createRequire } from "module";
+
+const _require = createRequire(import.meta.url);
+const { version } = _require("../package.json");
+
+const options: swaggerJsdoc.Options = {
+  definition: {
+    openapi: "3.0.3",
+    info: {
+      title: "DocFast API",
+      version,
+      description:
+        "Convert HTML, Markdown, and URLs to pixel-perfect PDFs. Built-in invoice & receipt templates.\n\n## Authentication\nAll conversion and template endpoints require an API key via `Authorization: Bearer <key>` or `X-API-Key: <key>` header.\n\n## Rate Limits\n- Free tier: 100 PDFs/month, 10 req/min\n- Pro tier: 5,000 PDFs/month, 30 req/min\n\n## Getting Started\n1. Try the demo endpoints (no auth required, 5/hour limit)\n2. Upgrade to Pro at [docfast.dev](https://docfast.dev)\n3. Use your API key to convert documents",
+      contact: {
+        name: "DocFast",
+        url: "https://docfast.dev",
+        email: "support@docfast.dev",
+      },
+    },
+    servers: [{ url: "https://docfast.dev", description: "Production" }],
+    tags: [
+      { name: "Demo", description: "Try the API without authentication (watermarked, 5/hour)" },
+      { name: "Conversion", description: "Convert HTML, Markdown, or URLs to PDF" },
+      { name: "Templates", description: "Built-in document templates" },
+      { name: "Account", description: "Signup and key recovery" },
+      { name: "Billing", description: "Stripe-powered subscription management" },
+      { name: "System", description: "Health checks and usage stats" },
+    ],
+    components: {
+      securitySchemes: {
+        BearerAuth: {
+          type: "http",
+          scheme: "bearer",
+          description: "API key as Bearer token",
+        },
+        ApiKeyHeader: {
+          type: "apiKey",
+          in: "header",
+          name: "X-API-Key",
+          description: "API key via X-API-Key header",
+        },
+      },
+      schemas: {
+        PdfOptions: {
+          type: "object",
+          properties: {
+            format: {
+              type: "string",
+              enum: ["A4", "Letter", "Legal", "A3", "A5", "Tabloid"],
+              default: "A4",
+              description: "Page size",
+            },
+            landscape: {
+              type: "boolean",
+              default: false,
+              description: "Landscape orientation",
+            },
+            margin: {
+              type: "object",
+              properties: {
+                top: { type: "string", example: "20mm" },
+                bottom: { type: "string", example: "20mm" },
+                left: { type: "string", example: "15mm" },
+                right: { type: "string", example: "15mm" },
+              },
+            },
+            printBackground: {
+              type: "boolean",
+              default: true,
+              description: "Print background graphics",
+            },
+            filename: {
+              type: "string",
+              default: "document.pdf",
+              description: "Suggested filename for the PDF",
+            },
+          },
+        },
+        Error: {
+          type: "object",
+          properties: {
+            error: { type: "string", description: "Error message" },
+          },
+        },
+      },
+    },
+  },
+  apis: ["./dist/routes/*.js", "./dist/index.js"],
+};
+
+export const swaggerSpec = swaggerJsdoc(options);