infra: self-hosted redis to replace upstash (~$75/mo → ~$2/mo) (#674)

* infra: add self-hosted redis config, remove upstash

Upstash was costing ~$75/month at 37M commands. Self-hosted Redis on
Fly will cost ~$2/month.

Changes:
- redis/fly.toml: Redis 7 Alpine with AOF persistence, 256MB VM
- redis/README.md: deployment and switchover instructions
- Remove upstash from costs script and frontend (redis cost is
included in fly_io since it's a Fly VM)

Deployment steps:
1. fly apps create plyr-redis
2. fly volumes create redis_data --region iad --size 1 -a plyr-redis
3. fly deploy -a plyr-redis (from redis/ dir)
4. fly secrets set DOCKET_URL=redis://plyr-redis.internal:6379 -a relay-api
5. Verify docket tasks work
6. fly redis destroy plyr-redis-prd

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[e-mail]>

* docs: update README costs and project structure for redis

---------

Co-authored-by: Claude Opus 4.5 <[e-mail]>

README.md

···
 │   └── src/routes/       # pages
 ├── moderation/           # Rust labeler service
 ├── transcoder/           # Rust audio service
+├── redis/                # self-hosted Redis config
 ├── docs/                 # documentation
 └── justfile              # task runner
 ```
···
 <details>
 <summary>costs</summary>
 
-~$35-40/month:
-- fly.io backend (prod + staging): ~$10/month
-- fly.io transcoder: ~$0-5/month (auto-scales to zero)
+~$20/month:
+- fly.io (backend + redis + moderation): ~$14/month
 - neon postgres: $5/month
-- audd audio fingerprinting: ~$10/month
-- cloudflare (pages + r2): ~$0.16/month
+- cloudflare (pages + r2): ~$1/month
+- audd audio fingerprinting: $5-10/month (usage-based)
+
+live dashboard: https://plyr.fm/costs
 
 </details>
 

frontend/src/routes/costs/+page.svelte

···
 				breakdown: CostBreakdown;
 				note: string;
 			};
-			upstash?: {
-				amount: number;
-				note: string;
-			};
 			audd: {
 				amount: number;
 				base_cost: number;
···
 					data.costs.fly_io.amount,
 					data.costs.neon.amount,
 					data.costs.cloudflare.amount,
-					data.costs.upstash?.amount ?? 0,
 					data.costs.audd.amount
 				)
 			: 1
···
 					</div>
 					<span class="cost-note">{data.costs.cloudflare.note}</span>
 				</div>
-
-				{#if data.costs.upstash}
-					<div class="cost-item">
-						<div class="cost-header">
-							<span class="cost-name">upstash</span>
-							<span class="cost-amount">{formatCurrency(data.costs.upstash.amount)}</span>
-						</div>
-						<div class="cost-bar-bg">
-							<div
-								class="cost-bar"
-								style="width: {barWidth(data.costs.upstash.amount, maxCost)}%"
-							></div>
-						</div>
-						<span class="cost-note">{data.costs.upstash.note}</span>
-					</div>
-				{/if}
 
 				<div class="cost-item">
 					<div class="cost-header">

redis/README.md

···
+# plyr-redis
+
+self-hosted Redis on Fly.io for docket background tasks.
+
+## deployment
+
+```bash
+# first time: create app and volume
+fly apps create plyr-redis
+fly volumes create redis_data --region iad --size 1 -a plyr-redis
+
+# deploy
+fly deploy -a plyr-redis
+```
+
+## connecting from other fly apps
+
+Redis is accessible via Fly's private network:
+
+```
+redis://plyr-redis.internal:6379
+```
+
+Update `DOCKET_URL` secret on backend apps:
+
+```bash
+fly secrets set DOCKET_URL=redis://plyr-redis.internal:6379 -a relay-api
+fly secrets set DOCKET_URL=redis://plyr-redis.internal:6379 -a relay-api-staging
+```
+
+## configuration
+
+- **persistence**: AOF (append-only file) enabled for durability
+- **memory**: 200MB max with LRU eviction
+- **storage**: 1GB volume mounted at /data
+
+## cost
+
+~$1.94/month (256MB shared-cpu VM) + $0.15/month (1GB volume) = ~$2.09/month
+
+vs. Upstash pay-as-you-go which was costing ~$75/month at 37M commands.

redis/fly.toml

···
+app = "plyr-redis"
+primary_region = "iad"
+
+[build]
+  image = "redis:7-alpine"
+
+[mounts]
+  source = "redis_data"
+  destination = "/data"
+
+[env]
+  # redis config via command line args in [processes]
+
+[processes]
+  app = "--appendonly yes --maxmemory 200mb --maxmemory-policy allkeys-lru"
+
+[[services]]
+  protocol = "tcp"
+  internal_port = 6379
+
+  # only accessible within private network
+  [[services.ports]]
+    port = 6379
+
+[[vm]]
+  memory = "256mb"
+  cpu_kind = "shared"
+  cpus = 1

scripts/costs/export_costs.py

···
 # fly.io: manually updated from cost explorer (TODO: use fly billing API)
 # neon: fixed $5/month
 # cloudflare: mostly free tier
-# upstash: free tier (256MB, 500K commands/month)
+# redis: self-hosted on fly (included in fly_io costs)
 FIXED_COSTS = {
     "fly_io": {
         "breakdown": {
···
         "domain": 1.00,
         "total": 1.16,
         "note": "r2 egress is free, pages free tier",
-    },
-    "upstash": {
-        "total": 0.00,
-        "note": "redis for docket + caching (free tier: 256MB, 500K commands/month)",
     },
 }
 
···
         plyr_fly
         + FIXED_COSTS["neon"]["total"]
         + FIXED_COSTS["cloudflare"]["total"]
-        + FIXED_COSTS["upstash"]["total"]
         + audd_stats["estimated_cost"]
     )
 
···
                     "domain": FIXED_COSTS["cloudflare"]["domain"],
                 },
                 "note": FIXED_COSTS["cloudflare"]["note"],
-            },
-            "upstash": {
-                "amount": FIXED_COSTS["upstash"]["total"],
-                "note": FIXED_COSTS["upstash"]["note"],
             },
             "audd": {
                 "amount": audd_stats["estimated_cost"],