Merge pull request 'feat(suggest): school autosuggest, and the rate-limit fix it needed first' (#127) from feat/school-autosuggest into main

Reviewed-on: #127

docs/DEPLOY.md

@@ -151,6 +151,36 @@ needed), and fails the check only when a finding is rated
 **severe** (would break prod, leak data, or corrupt data). Minor findings are
 informational and never block a merge.
 
+## Rate limiting, and the Cloudflare gap
+
+Two independent limits protect the API:
+
+- **Per client**, via slowapi, keyed on `CF-Connecting-IP` (falling back to
+  `X-Forwarded-For`, then the peer address). 60/minute by default;
+  `/api/suggest` gets 120/minute because typing is bursty.
+- **Globally**, via `GlobalRateLimitMiddleware`: a fixed 60-second window over
+  all `/api/` traffic, `GLOBAL_RATE_LIMIT_PER_MINUTE` (default 3000),
+  independent of any client identity. Requests from `127.0.0.1` are exempt so
+  the container healthcheck cannot be starved into a restart loop.
+
+### Open: the origin must only accept Cloudflare
+
+`CF-Connecting-IP` is only meaningful for requests that actually reached the
+origin through Cloudflare, and **the application cannot verify that they did**.
+Anything able to reach the origin directly can set that header freely and, by
+rotating it, mint a fresh rate-limit bucket per request — defeating per-client
+limits on every endpoint.
+
+The global ceiling bounds the damage to total origin capacity. It does not fix
+the underlying gap, and nothing in the code can. Closing it needs one of:
+
+- **Authenticated Origin Pulls** — Cloudflare presents a client certificate the
+  origin requires, so non-Cloudflare traffic is refused at TLS.
+- **An origin firewall** restricted to Cloudflare's published IP ranges.
+
+Until one is in place, treat per-client limits as protection against accidents
+and ordinary load, not against a determined caller.
+
 ## Feature flags (Unleash)
 
 Flag state lives in a self-hosted Unleash instance, deployed as its own