web: fix apis to use consistently use camel case (#802)

.claude/projects/-home-user--src-l5yth-potato-mesh/memory/MEMORY.md

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+# Memory index
+
+- [Web app local run](web-app-local-run.md) — rackup fails (no config.ru); use `ruby app.rb`, binds 41447
+- [API casing & federation signature](api-casing-and-federation-signature.md) — federation wire is camelCase because it's signed; read API is snake_case; don't rename signed keys

.claude/projects/-home-user--src-l5yth-potato-mesh/memory/api-casing-and-federation-signature.md

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+---
+name: api-casing-and-federation-signature
+description: API JSON casing map + the camelCase federation-signature landmine
+metadata:
+  type: project
+---
+
+**Federation instance signatures are computed over camelCase canonical keys.**
+`web/lib/potato_mesh/application/federation/signature.rb` `canonical_instance_payload`
+signs `JSON.generate({contactLink, id, domain, pubkey, name, version, channel,
+frequency, latitude, longitude, lastUpdateTime, isPrivate}, sort_keys: true)`. So
+the federation wire — `/.well-known/potato-mesh`, `GET /api/instances`
+(`instances.rb` `normalize_instance_row`), the announcement payload
+(`self_instance.rb`) — **must stay camelCase**. Renaming any signed key breaks
+cross-version signature verification **bilaterally** (no "emit both keys" shim
+fixes a signature). Treat this as immovable without a signature-version scheme.
+
+**HTTP API casing map (as of 0.7.0):**
+- Read collections (`/api/nodes`, `/api/messages`, `/api/positions`,
+  `/api/telemetry`, `/api/traces`, `/api/neighbors`) and `/api/stats`: **snake_case**
+  already (`query_nodes` selects snake columns; matrix reads `rx_time`).
+- `/version`: **snake_case** since 0.7.0 (was the lone camelCase read response).
+- `POST /api/nodes` **input**: Meshtastic camelCase, but `upsert_node` now also
+  accepts snake via nil-aware `pick_alias` (camel preferred → ingestor unaffected).
+- Federation wire: **camelCase** (signed — see above).
+
+**Gotchas that cost time:**
+- `/api/nodes` camelCase you see in the frontend is the POST input, the client
+  `normalizeNodeCollection` internal model, and `?? shortName` fallbacks — NOT the
+  GET response. Don't "snake-case /api/nodes"; it already is.
+- The dashboard frontend reads config from the server-rendered `data-app-config`
+  attribute (`views/layouts/app.erb`, helper `frontend_app_config`), **not** from
+  `/version`. The matrix bridge only pings `/version` for liveness (no key reads).
+  The Flutter app *does* read `/version` config keys (`app/lib/main.dart`) — the
+  one consumer that breaks on a `/version` casing change.
+
+See [[web-app-local-run]] for running the server to curl these.