chore: seminarhof customer project

CLAUDE.md

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+# Project conventions
+
+## Error handling
+
+Always use **defined error classes** for caught / expected exceptions — never
+`throw new Error('some_string')`.
+
+- Domain errors live in `packages/functions/src/errors.ts`. Each extends a
+  Pikku core error (`BadRequestError`, `ConflictError`, `ForbiddenError`,
+  `NotFoundError`, …) and is registered with `addError(...)` so it maps to the
+  correct HTTP status and a stable client-facing code.
+- Raw `throw new Error(...)` is only acceptable for truly unexpected,
+  programmer-error conditions that should surface as a 500.
+- Validation/contract failures (bad params, illegal state transitions, etc.)
+  must be a defined error so callers can branch on the type and the client
+  receives a meaningful status + message.
+
+## Sessions (optional auth everywhere)
+
+`sessionCookieMiddleware` is registered globally (`addHTTPMiddleware('*', …)`
+in `wirings/middleware.ts`), so the session cookie is resolved on **every**
+route — including `auth: false` / `pikkuSessionlessFunc` endpoints.
+
+- In a sessionless function, read the optional session from the third arg:
+  `func: async (services, input, { session }) => { const s = await session?.get(); … }`.
+  `s` is `undefined` for anonymous callers and the `UserSession`
+  (`{ userId, role }`) for logged-in ones.
+- This lets a public endpoint vary its response by viewer role (e.g. show
+  admins more than anonymous visitors) without a separate authenticated route.
+- Use `pikkuFunc` (required session, third arg `{ session }` non-optional) only
+  when the route must reject anonymous callers outright.
+
+## Database changes (Pikku DB-first pipeline)
+
+Schema changes go **DB-first**, in this order — doing it code-first breaks the
+Pikku inspector / generated types:
+
+1. Edit the SQL (`db/sqlite/*.sql`, `db/sqlite-seed.sql`).
+2. Regenerate: `yarn db:reset && yarn db:migrate`
+   (`pikku db migrate` refreshes `.pikku/db/schema.d.ts` and the generated
+   zod at `.pikku/db/zod.gen.ts`, imported as `#pikku/db/zod.gen.js`).
+3. Update backend function logic against the new types.
+4. Regenerate the client SDK: `yarn workspace @project/functions pikku all`.
+5. Update the frontend / consumers.
+
+This is a pre-production project — edit migrations in place rather than
+appending compatibility migrations.