feat(cache): PG kv_cache ported from MP TTLCache, TMDB request and recognize caches

Migration 0042_cache adds UNLOGGED kv_cache. PgCache mirrors MP
runtime/cache.py (region, per-key TTL, TLRU maxsize eviction, @cached as
cachedCall); only the storage moves from memory to PG. TMDB request
responses (MP TMDb.request @cached) and recognize results (MP TmdbCache:
same key, {id:0} negative cache with EMPTY_RESULT_CACHE_TTL, type-conflict
checks, backfill after manual assignment) live in kv_cache, shared by all
processes. Settings cache.tmdbTtlHours / tmdbMaxSize / emptyResultTtlSec
map to META_CACHE_EXPIRE / CONF.tmdb / EMPTY_RESULT_CACHE_TTL. TMDB
details now also store posterPath / backdropPath.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/db/migrations/0042_cache.ts

@@ -0,0 +1,30 @@
+import type { Kysely } from "kysely";
+import { dropTables, execDdl } from "../src/migration-helpers.ts";
+
+// C2-A 缓存:移植 MP app/runtime/cache.py 的 TTLCache(cachetools TLRUCache:按 region 分区、每个 key 独立 TTL、
+// maxsize 超限先删过期再删最久未用),存储从进程内存换成 PG UNLOGGED 表(不写 WAL,崩溃后清空,正合缓存语义),三进程共享。
+// expires_at 过期即视为未命中;accessed_at 为最近读写时间(LRU 依据);定时任务 cache.sweep 每 10 分钟删过期行。
+
+// biome-ignore lint/suspicious/noExplicitAny: 迁移不依赖应用表类型
+export async function up(db: Kysely<any>): Promise<void> {
+  await execDdl(
+    db,
+    `
+create unlogged table kv_cache (
+  region text not null,
+  key text not null,
+  value jsonb not null,
+  expires_at timestamptz not null,
+  updated_at timestamptz not null default now(),
+  accessed_at timestamptz not null default now(),
+  primary key (region, key)
+);
+create index kv_cache_expires_idx on kv_cache (expires_at);
+`,
+  );
+}
+
+// biome-ignore lint/suspicious/noExplicitAny: 同上
+export async function down(db: Kysely<any>): Promise<void> {
+  await execDdl(db, dropTables(["kv_cache"]));
+}