docs(homelab): add TAPIR_FETCH_BACKOFF config, update snapshot date

docs/homelab-integration.md

@@ -2,7 +2,7 @@
 
 The concrete endpoints, conventions, and identifiers Tapir depends on, so an independent
 session doesn't have to rediscover them. **Verify anything marked "confirm" before relying on
-it** — endpoints and aliases drift, and this file is a snapshot (2026-06-02), not a live source.
+it** — endpoints and aliases drift, and this file is a snapshot (2026-06-06), not a live source.
 
 ## Local AI (the Primary in `llm.Router`)
 
@@ -160,7 +160,7 @@ allow per-provider when a user connects one.
 
 ---
 
-_Snapshot date 2026-06-02. Items marked **confirm** were not verified to a pinned source at
+_Snapshot date 2026-06-06. Items marked **confirm** were not verified to a pinned source at
 snapshot time — check brain or the live cluster before depending on them._
 
 ## Stage 1 — multi-user facts (verified 2026-06-03)
@@ -194,7 +194,7 @@ snapshot time — check brain or the live cluster before depending on them._
 
 ## Scheduled discovery (ADR-018, verified 2026-06-05)
 
-`tapir serve` runs discovery for **all users** in-process on a timer (no CronJob). Two env
+`tapir serve` runs discovery for **all users** in-process on a timer (no CronJob). Three env
 knobs plus one load-bearing deployment constraint:
 
 - `TAPIR_DISCOVERY_INTERVAL` — Go duration, e.g. `2h`. The cadence the serve process runs a
@@ -205,6 +205,11 @@ knobs plus one load-bearing deployment constraint:
   click-path — serialises through this one limiter so the pod cannot collectively trip 429s. `0`
   = unlimited (dev/tests). This is the precondition that makes auto-summarize-on-a-schedule safe;
   do not raise it aggressively without watching for 429s.
+- `TAPIR_FETCH_BACKOFF=4h` — per-video rate-limit retry window; default `1h`. A video that
+  returns HTTP 429 on a caption fetch is skipped for this duration before being retried. The
+  scheduler checks `NOW() - rate_limited_at > TAPIR_FETCH_BACKOFF` before attempting to fetch
+  a video marked `transcript_status = rate_limited`. Longer values reduce 429 pressure at the
+  cost of slower recovery after a throttling episode.
 - **SINGLE-REPLICA WARNING (load-bearing).** The scheduler lives in the web process, so
   `replicas: 1` in the deployment manifest is load-bearing: running `tapir serve` at >1 replica
   makes **every** replica run the discovery loop → every user fetched in parallel from the same