#7 Ingest HTTPS endpoint: accept report POST, size limit

Add internal/ingest implementing POST /v1/reports, wired into the core
build-tag-free handler so the same route serves on the dev server and the
Cloudflare Worker.

Response contract (ADR #6 §2.4):
- 202 Accepted for valid JSON within the 256 KiB cap ({"status":"accepted"})
- 413 for oversized bodies (Content-Length fast path AND a MaxBytesReader
  hard cap, so a missing/lying Content-Length cannot bypass the limit)
- 415 when Content-Type is not application/json
- 400 for malformed JSON or failed schema validation (generic error body,
  never echoes request content)
- 405 with Allow: POST for any non-POST method
- 503 when the storage Sink fails

Storage is decoupled behind a small Sink interface (Store(ctx, raw)) with a
NopSink default and a MemorySink for tests, so PII scrubbing (#8) and
encrypted R2 storage (#9) can slot in without touching the HTTP contract.
Rate limiting (429) and volumetric shedding stay a Cloudflare-edge/Pulumi
concern per #2 and are intentionally not implemented in the Worker.

Tests:
- Go unit tests (net/http/httptest) for every response code, including 413
  via both Content-Length and an oversized streamed body, plus boundary,
  storage-failure, and no-content-echo cases.
- Bruno API tests in OpenCollection YAML format under api-tests/, asserting
  the full contract against the local dev server via @usebruno/cli.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/handler/handler.go

@@ -11,20 +11,29 @@ package handler
 import (
 	"encoding/json"
 	"net/http"
+
+	"github.com/JMR-dev/LibreMail-Bug-Report-Ingest/internal/ingest"
 )
 
 // serviceName identifies this service in responses.
 const serviceName = "libremail-bug-report-ingest"
 
-// New returns an http.Handler serving the bootstrap health/hello endpoints:
+// New returns an http.Handler serving the ingest Worker's endpoints:
 //
-//	GET /         -> 200, JSON service/status/message
-//	GET /healthz  -> 200, JSON {"status":"ok"}
+//	GET  /            -> 200, JSON service/status/message
+//	GET  /healthz     -> 200, JSON {"status":"ok"}
+//	POST /v1/reports  -> 202 on accept; 400/413/415/405/503 per the ingest contract
 //
-// Any other path returns 404 and any non-GET method returns 405.
+// Any other path returns 404. On the health/hello endpoints any non-GET method
+// returns 405; on /v1/reports any non-POST method returns 405 (Allow: POST).
+//
+// The ingest endpoint is wired with a NopSink for now: it enforces the full
+// HTTP contract (size cap + schema validation) but discards accepted bodies
+// until the real storage sink (scrub + encrypt + R2) lands in #8/#9.
 func New() http.Handler {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/healthz", healthz)
+	mux.Handle("/v1/reports", ingest.NewHandler(ingest.NopSink{}))
 	mux.HandleFunc("/", root)
 	return mux
 }