Added CLAUDE.md and development rules for Claude Code.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.claude/rules/backend.md

@@ -0,0 +1,54 @@
+---
+paths:
+  - "src/backend/**"
+  - "src/main.rs"
+  - "src/error.rs"
+  - "src/config.rs"
+---
+
+# Backend rules
+
+## Server functions
+
+- One file per domain in `src/backend/`. Server-only helpers and their imports go in the `cfg_if! { if #[cfg(feature = "ssr")] { ... }}` block at the top; `#[server]` functions follow below it. Extra server-only imports inside a server fn body are written as local `use` statements.
+- Use plain `#[server]` for new functions (older ones spell out `#[server(Name, "/api", "Url", "name")]`; both end up under `/api`).
+- Return `Result<ApiResponse<T>, ServerFnError>`. Expected/business failures are `Ok(ApiResponse::Error("English message".to_string()))` — the client passes that string through `trl()`, so add it to the catalogue. `Err(ServerFnError)` is for real failures (DB down etc.).
+- A function used with `<DataForm>` / `<QuestionDialog>` must return `ApiResponse<()>` and take the form entity as a single struct argument; its name is the prefix of the form field names (`company: Company` ↔ `name="company[name]"`).
+- For `<DataForm>`, implement `ForValidation` for the generated struct (PascalCase of the fn name) right below the function:
+
+  ```rust
+  impl ForValidation for UpdateCompany {
+      fn entity(&self) -> &dyn Validate { &self.company }
+  }
+  ```
+
+  That only validates in the browser. Anything that matters must be checked again inside the server fn.
+
+## Authorization
+
+- Every server fn that reads or changes non-public data starts with `perm_check!(is_logged_in)` or `perm_check!(is_admin)`; use `user_check!(login)` when a non-admin may only touch their own record. The macros return early with 403 and `ApiResponse::Error`, so they only work in functions returning `Result<ApiResponse<_>, _>`.
+- The auth middleware protects only `/admin*` page requests. `/api/*` is not covered by it — a server fn without `perm_check!` is public. Only the public booking form endpoints should be.
+- Plain Actix handlers (like `appearance::upload`) must check the session themselves.
+- The logged-in `User` is stored in the cookie session under `"user"`; read it with `logged_in_user()`.
+
+## Database access
+
+- Get the pool with `get_pool().await?` (and the mailer with `get_mailing().await?`); they come from `AppData` in Actix app data.
+- Runtime-checked sqlx only: `query` / `query_as::<_, T>` with `$n` binds. No `query!` macros (there is no `DATABASE_URL`/offline data at build time).
+- Always bind values; never format user input into SQL.
+- Multi-statement writes go through a transaction (`pool.begin()`, helpers take `&mut Transaction<'_, Postgres>`), as in `create_reservation`.
+- The users table is `"user"` — always quoted.
+
+## Data types (`data.rs`)
+
+- Types crossing the server/client boundary live in `src/backend/data.rs` and must compile for WASM: sqlx derives only as `#[cfg_attr(feature = "ssr", derive(sqlx::FromRow))]` / `sqlx::Type`.
+- `id` fields are private with an `id()` getter; other fields are mostly `pub`.
+- Validation uses `validator` 0.16 derive attributes; every `message = "..."` is an English translation key.
+- Rust enums mapped to Postgres enums (`SlotType`, `ReservationState`, `MessageType`) must keep variant names identical to the SQL enum labels.
+
+## Errors, logging, mail
+
+- Server-side helpers return `AppError`; add a `From` impl in `src/error.rs` for new error sources (ssr-only ones behind `#[cfg(feature = "ssr")]`). The `From` impls already log the error.
+- Log with the `log` macros (`info!`, `warn!`, `error!`), not `println!`.
+- Send mail through `Mailer::send_mail` (queued to a background sender thread), never directly from a request. Templates are `message` rows keyed by `MessageType` with `#date#` and `#summary#` placeholders.
+- A new `[section]`/key in `config.toml` needs the struct in `src/config.rs` and an entry in `config_sample.toml`.