Add active listings tab from RentCast API

- update_listings.R: pulls 1-mile radius, clips to plat boundary
- Listings tab: table with listed date, address, sqft, price, $/sqft
- Weekly cron: Sunday 11:30pm (30 min after owners refresh)
- httr2 added to renv.lock

data-raw/update_listings.R

@@ -0,0 +1,68 @@
+# update_listings.R
+# Weekly update: pull active listings from RentCast within 1 mile of
+# St. Andrews center, clip to plat boundary, save data/listings.rds.
+# Input:  .Renviron (RENTCAST_API_KEY)
+#         data/plats/plats.shp
+# Output: data/listings.rds
+
+library(httr2)
+library(jsonlite)
+library(sf)
+library(dplyr)
+
+# ── API key ───────────────────────────────────────────────────────────────────
+api_key <- Sys.getenv("RENTCAST_API_KEY")
+if (identical(api_key, "")) stop("Missing RENTCAST_API_KEY in .Renviron")
+
+# ── Pull listings ─────────────────────────────────────────────────────────────
+resp <- request("https://api.rentcast.io/v1/listings/sale") |>
+  req_headers(
+    "Accept"    = "application/json",
+    "X-Api-Key" = api_key
+  ) |>
+  req_url_query(
+    latitude  = 27.076199,
+    longitude = -82.362253,
+    radius    = 1,
+    status    = "Active",
+    limit     = 500
+  ) |>
+  req_retry(max_tries = 3) |>
+  req_perform()
+
+if (resp_status(resp) >= 400)
+  stop("RentCast API error: HTTP ", resp_status(resp), "\n", resp_body_string(resp))
+
+listings_raw <- jsonlite::fromJSON(resp_body_string(resp), flatten = TRUE)
+cat("Fetched:", nrow(listings_raw), "listings\n")
+
+# ── Clip to St. Andrews plat boundary ────────────────────────────────────────
+plats <- sf::st_read("./data/plats/plats.shp", quiet = TRUE) |>
+  sf::st_union()
+
+listings_sf <- sf::st_as_sf(
+  listings_raw,
+  coords = c("longitude", "latitude"),
+  crs    = 4326,
+  remove = FALSE
+)
+
+in_plat  <- lengths(sf::st_within(listings_sf, plats)) > 0
+listings <- listings_raw[in_plat, ]
+cat("After plat clip:", nrow(listings), "listings\n")
+
+# ── Select and clean columns ──────────────────────────────────────────────────
+listings <- listings |>
+  transmute(
+    listed_date   = as.Date(listedDate),
+    address       = formattedAddress,
+    sqft          = as.numeric(squareFootage),
+    price         = as.numeric(price),
+    price_per_sqft = round(price / sqft, 0),
+    latitude,
+    longitude
+  ) |>
+  arrange(desc(listed_date))
+
+cat("Listings saved:", nrow(listings), "\n")
+saveRDS(listings, "./data/listings.rds")