feat: Slack → Buzz workspace migration

.env.example

@@ -58,6 +58,10 @@ RELAY_URL=ws://localhost:3000
 # the web frontend at / for browser requests. Leave unset for local dev
 # (use `just web` for Vite HMR instead).
 # BUZZ_WEB_DIR=./web/dist
+# Maximum accepted age of an event's created_at in seconds (default 900).
+# Future drift stays fixed at +15 min. Raise temporarily to run a history
+# import (e.g. `buzz import slack` — see docs/slack-import.md), then restore.
+# BUZZ_MAX_PAST_DRIFT_SECS=900
 
 # Shared Redis-backed admission limits. Defaults shown below; each value must
 # be a positive integer.

Cargo.toml

@@ -18,6 +18,7 @@ members = [
     "crates/buzz-workflow",
     "crates/buzz-media",
     "crates/buzz-cli",
+    "crates/buzz-migrate",
     "crates/buzz-pairing-cli",
     "crates/buzz-sdk",
     "crates/buzz-persona",
@@ -95,7 +96,7 @@ thiserror = "2"
 anyhow    = "1"
 
 # Utilities
-uuid    = { version = "1", features = ["v4", "serde"] }
+uuid    = { version = "1", features = ["v4", "v5", "serde"] }
 chrono  = { version = "0.4", features = ["serde"] }
 
 # HTTP client (webhook delivery)
@@ -106,6 +107,7 @@ sha2      = "0.11"
 hex       = "0.4"
 hmac      = "0.13"
 base64    = "0.22"
+ring      = "0.17"
 
 # Randomness
 rand = "0.10"