Seed five curated, read-only post-processing templates so a non-expert gets
instant good-looking output before discovering the filter pipeline. Each is an
opinionated chain of existing filters (auto-crop/saturation/contrast/colour-
temperature/temporal-blur) tuned for a use case (films, games, evening ambience,
low-flicker, crisp cool-white).
Mirrors the built-in-gradient pattern: adds is_builtin to PostprocessingTemplate,
seeds missing looks on store init (idempotent, additive — no migration), and
makes built-ins read-only (update/delete raise -> 400; clone to customise).
Surfaced via the existing template picker + is_builtin in the response/type.
7 unit tests (seeding, idempotency, read-only protection, round-trip); full
suite green (1926 passed). (A runtime intensity slider is a follow-up — it needs
a filter-chain parameterisation layer.)
alexei.dolgolyov
e18d56c838