feat: add REDIS_KEY_PREFIX env var for Redis ACL namespace isolation (#365)

* feat: add REDIS_KEY_PREFIX env var for Redis ACL namespace isolation

Adds optional REDIS_KEY_PREFIX env var that prefixes all Redis keys
(BullMQ queues via `prefix` option, cache/lock/rate-limit keys via
`redisKey()` helper). When unset, behavior is unchanged (BullMQ
defaults to "bull:", cache keys are unprefixed).

This enables self-hosters using Redis ACL multi-tenancy to restrict
useSend to its own key namespace (e.g. `~usesend:*`).

16 files changed across env schema, Redis module, 9 BullMQ queue/worker
files, and 5 direct Redis key operation sites.

* docs: add REDIS_KEY_PREFIX to self-host assets and fix docker run example

Add REDIS_KEY_PREFIX env var to docker/prod/compose.yml, .env.example,
.env.selfhost.example, and self-hosting docs. Fix missing trailing
backslashes in standalone docker run example.

* fix(redis): disable ioredis ready check and BullMQ version check

Redis ACL blocks INFO command (in @dangerous category). ioredis uses
INFO for ready check, BullMQ uses it for version detection. Without
these flags, BullMQ workers fail to initialize and silently stop
processing jobs.

- Add enableReadyCheck: false to ioredis connection
- Add skipVersionCheck: true to all 5 Queue + 5 Worker constructors

* fix(redis): add skipVersionCheck to remaining BullMQ job queues

Add skipVersionCheck: true to Queue and Worker constructors in all 4 job
files (campaign-scheduler, cleanup-email-bodies, usage-job,
webhook-cleanup) to match the pattern already used in service files.
This prevents BullMQ version mismatch errors when using REDIS_KEY_PREFIX
with Redis ACL namespace isolation.

apps/web/src/env.js

@@ -53,6 +53,7 @@ export const env = createEnv({
     FOUNDER_EMAIL: z.string().optional(),
     DISCORD_WEBHOOK_URL: z.string().optional(),
     REDIS_URL: z.string(),
+    REDIS_KEY_PREFIX: z.string().default(""),
     S3_COMPATIBLE_ACCESS_KEY: z.string().optional(),
     S3_COMPATIBLE_SECRET_KEY: z.string().optional(),
     S3_COMPATIBLE_API_URL: z.string().optional(),
@@ -116,6 +117,7 @@ export const env = createEnv({
     FOUNDER_EMAIL: process.env.FOUNDER_EMAIL,
     DISCORD_WEBHOOK_URL: process.env.DISCORD_WEBHOOK_URL,
     REDIS_URL: process.env.REDIS_URL,
+    REDIS_KEY_PREFIX: process.env.REDIS_KEY_PREFIX,
     FROM_EMAIL: process.env.FROM_EMAIL,
     S3_COMPATIBLE_ACCESS_KEY: process.env.S3_COMPATIBLE_ACCESS_KEY,
     S3_COMPATIBLE_SECRET_KEY: process.env.S3_COMPATIBLE_SECRET_KEY,