feat: production hardening and code separation

- Stack-allocate request bodies ≤64KB to avoid malloc in hot path
- Only cache body if module exports on_request_body handler
- Track heap allocation in proxy_ctx for correct cleanup
- Split proxy_wasm.c (2670→1256 lines) into focused modules:
  - proxy_wasm_mem.h: shared memory helper inlines
  - proxy_wasm_headers.c: header map operations
  - proxy_wasm_properties.c: property get/set
  - proxy_wasm_http.c: HTTP callout with anti-IP-rebinding
- All 16 tests passing

Author: RamazanKara

Dockerfile

@@ -17,7 +17,7 @@ RUN apt-get update && apt-get install -y \
     xz-utils \
     && rm -rf /var/lib/apt/lists/*
 
-# Install Varnish 8.0 from packagecloud
+# Install Varnish 8.0 (latest open-source release) from packagecloud
 RUN curl -fsSL https://packagecloud.io/varnishcache/varnish80/gpgkey \
        | gpg --dearmor -o /usr/share/keyrings/varnish.gpg \
     && echo "deb [signed-by=/usr/share/keyrings/varnish.gpg] https://packagecloud.io/varnishcache/varnish80/debian/ bookworm main" \

src/Makefile.am

@@ -11,6 +11,10 @@ libvmod_wasm_la_SOURCES = \
 	host_functions.h \
 	proxy_wasm.c \
 	proxy_wasm.h \
+	proxy_wasm_mem.h \
+	proxy_wasm_headers.c \
+	proxy_wasm_properties.c \
+	proxy_wasm_http.c \
 	proxy_wasm_shared.c \
 	proxy_wasm_shared.h