Speed up timeline load with portrait thumbs, bootstrap API, and caching.

Add catalog bootstrap endpoint, portrait thumbnail pipeline, lazy queued timeline images, gzip compression, and 3D texture throttling with code-split VirtualGallery.

db/migrate-perf-indexes.sql

@@ -0,0 +1,4 @@
+-- Query performance for timeline filters and influence lookups
+CREATE INDEX IF NOT EXISTS idx_artists_birth_year ON artists(birth_year);
+CREATE INDEX IF NOT EXISTS idx_artists_death_year ON artists(death_year);
+CREATE INDEX IF NOT EXISTS idx_influence_sources_source_painting ON painting_influence_sources(source_painting_id);