feat(app): FastAPI routes for the dispatcher + wire codec

[estebanzimanyi]

Summary

Step 5 of the MobilityAPI ingestion plan: exposes the catalog-driven Dispatcher (#6) + WireCodec (#7) as HTTP endpoints via FastAPI.

File	Purpose
mobilityapi/app.py	create_app(dispatcher, codec) factory; no global singletons.
mobilityapi/routers/catalog.py	GET /catalog (list) + GET /catalog/{name} (one signature).
mobilityapi/routers/functions.py	POST /functions/{name} — invoke with JSON body, decode/encode opaque MEOS types via the codec.
tests/test_app.py	11 HTTP-level tests via Starlette TestClient.

Route contract

POST /functions/{name}

Request:

{ "params": { "<arg>": <wire_value>, ... } }

Response (serialised return):

{ "result": "<wire_value>", "encoding": "mfjson" }

Response (scalar return):

{ "result": <value>, "encoding": null }

Error mapping

Status	Cause
404	Function name not in dispatcher catalog
400	Missing / extra parameters; param encoding has no codec decoder
500	Result encoding has no codec encoder

Flow

POST /functions/{name}  ──┐
                          │ 1. Decode opaque-type params
                          │    via codec.decode(encoding, wire_value)
                          ▼
                       Dispatcher.dispatch(name, decoded_params)
                          │ 2. Resolver returns a Python callable
                          │    (pymeos.functions.{name} in prod;
                          │     stub in tests).
                          ▼
                       result
                          │ 3. Encode the result via
                          │    codec.encode(encoding, value)
                          │    if catalog marks return as serialised.
                          ▼
                      InvokeResponse(result=…, encoding=…)

Step in the ingestion plan

This is step 5 of the plan documented in docs/MEOS_API_INGESTION_PLAN.md:

1. ✅ Plan + missing-work scope — docs: MobilityAPI ingestion plan for MEOS-API output + OpenAPI missing-work integration #3
2. ✅ Vendor MEOS-API artefacts — chore(vendor): vendor the MEOS-API artefacts #4
3. ✅ Vendor-drift CI workflow — ci(vendor): add a vendor-drift workflow #5
4. ✅ Dispatcher foundation — feat(dispatcher): catalog-driven MEOS-function dispatcher #6
5. ✅ WireCodec + resolvers — feat(resolvers,wire): pluggable resolvers + wire-layer codec #7
6. ✅ FastAPI routes (this PR)
7. Migrate first resource/* endpoint to use Dispatcher (follow-up)

Tests

$ python3 -m pytest tests/test_app.py tests/test_dispatcher.py tests/test_resolvers.py tests/test_wire.py
38 passed in 0.37s

11 new HTTP tests cover:

• /catalog lists exposable functions (sorted by name)
• /catalog/{name} returns full signature; 404 on unknown
• /functions/{name} invokes scalar, serialised-in/scalar-out, serialised-in/serialised-out shapes
• 404 on unknown function; 400 on missing param; 400 on extra param
• 400 on serialised param whose encoding has no decoder

Depends on

• chore(vendor): vendor the MEOS-API artefacts #4 — vendored MEOS-API artefacts (catalog)
• feat(dispatcher): catalog-driven MEOS-function dispatcher #6 — Dispatcher
• feat(resolvers,wire): pluggable resolvers + wire-layer codec #7 — WireCodec + resolvers