M2a: server workspace, kvitt-domain, skeleton routes, OpenAPI match, Dockerfile

Cargo workspace (kvitt-domain, kvitt-server, kvitt-import), Rust 1.99.1 pinned.
kvitt-domain passes every Rust vector and adds next_occurrence_date (D-015).
kvitt-server: config, SQLite pool (WAL, §8.9 pragmas), migration 0001 identical to
the contract schema, error type for all 25 codes, auth extractor and protocol
layer, all 33 routes (E-1/E-2 implemented, the rest 501), utoipa document equal
to contracts/openapi.yaml, seams for M3/M4/M9, serve/migrate/healthcheck.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/crates/kvitt-domain/src/lib.rs

@@ -0,0 +1,39 @@
+//! Kvitt domain rules as pure functions (SPEC §9.1, §9.3, §9.4, §9.5 `next_occurrence_date`, §14.5).
+//!
+//! No I/O, no clock, no randomness, no locale. Ids are plain strings (the test vectors use short ids like `"a"`);
+//! money is `i64` öre and basis points are `u32`. The Kotlin `:domain` module implements the same functions and both
+//! must pass every vector in `contracts/test-vectors/` (`tests/vectors.rs`).
+
+// No unwrap/expect outside tests (CLAUDE.md server rule); integration tests are separate crates and may use them.
+#![cfg_attr(not(test), deny(clippy::unwrap_used, clippy::expect_used))]
+
+mod allocation;
+mod balance;
+mod recurring;
+mod settlement;
+mod split;
+
+pub use allocation::{
+    AccountPosition, Allocation, AllocationError, AllocationProposal, over_settled_accounts,
+    propose_allocation,
+};
+pub use balance::{BalanceExpense, BalanceSettlement, Balances, compute_balances};
+pub use recurring::{
+    Period, RecurrenceError, RecurrenceSchedule, next_candidate_period, next_occurrence_date,
+};
+pub use settlement::{SettlementError, validate_settlement};
+pub use split::{SplitError, SplitSpec, compute_split};
+
+/// Smallest valid amount of an expense, settlement or template, in öre (SPEC §9.6).
+pub const AMOUNT_MIN_ORE: i64 = 1;
+/// Largest valid amount of an expense, settlement or template, in öre: 10 000 000,00 kr (SPEC §9.6).
+pub const AMOUNT_MAX_ORE: i64 = 1_000_000_000;
+/// 100 % in basis points.
+pub const BP_TOTAL: u32 = 10_000;
+/// Most allocations one settlement may have (SPEC §9.6).
+pub const MAX_ALLOCATIONS: usize = 50;
+
+/// Whether `amount_ore` is within SPEC §9.6 (1 to 1 000 000 000).
+pub fn amount_in_range(amount_ore: i64) -> bool {
+    (AMOUNT_MIN_ORE..=AMOUNT_MAX_ORE).contains(&amount_ore)
+}