chore: replace hand-rolled layout() with @fastify/view + EJS

Convert all src/views/*.ts template-literal modules to .ejs templates
under views/. Register @fastify/view plugin in server.ts with EJS
engine and _layout.ejs as the layout file. Update route handlers to
use reply.view() instead of reply.send(layout(...)). Delete the old
TypeScript view modules and layout.ts.

Closes #19

package.json

@@ -23,15 +23,18 @@
     "@fastify/multipart": "^9.4.0",
     "@fastify/rate-limit": "^10.3.0",
     "@fastify/static": "^9.0.0",
+    "@fastify/view": "^11.1.1",
     "bchen-sqlite-migrate": "git+https://gitea.bchen.dev/brendan/sqlite-migrate.git#v0.1.0",
     "bcrypt": "^6.0.0",
     "better-sqlite3": "^12.6.2",
+    "ejs": "^5.0.2",
     "fastify": "^5.7.4",
     "nanoid": "^5.1.6"
   },
   "devDependencies": {
     "@types/bcrypt": "^6.0.0",
     "@types/better-sqlite3": "^7.6.13",
+    "@types/ejs": "^3.1.5",
     "@types/node": "^25.3.3",
     "tsx": "^4.21.0",
     "typescript": "^5.9.3",