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/Cargo.toml

@@ -0,0 +1,12 @@
+[workspace]
+resolver = "3"
+members = ["crates/kvitt-domain", "crates/kvitt-server", "crates/kvitt-import"]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2024"
+rust-version = "1.99"
+publish = false
+
+[workspace.lints.rust]
+unsafe_code = "forbid"