Fix color extraction and image cache setup in development

Move `ensureImageDirs` outside the production-only block so the local
image cache directories are created in dev mode too. Update
`extractAndStoreColors` to download the poster if it isn't cached yet
instead of falling back to a direct TMDB CDN URL, keeping color
extraction consistent with the server-side image routing approach. Add
`/data` to `.gitignore` to avoid committing the local cache directory.

lib/db/client.ts

@@ -9,7 +9,7 @@ const globalForDb = globalThis as unknown as {
 
 if (!globalForDb._client) {
   globalForDb._client = createClient({
-    url: process.env.DATABASE_URL ?? "file:sqlite.db",
+    url: process.env.DATABASE_URL ?? "file:./data/sqlite.db",
   });
   globalForDb._client.execute("PRAGMA journal_mode = WAL");
   globalForDb._client.execute("PRAGMA foreign_keys = ON");