build: switch to hybrid build for Kotlin/JS web-app and optimize Docker setup

Replaced multi-stage Docker builds with a hybrid approach that pre-builds frontend artifacts locally and copies them into the container. Removed Kotlin Multiplatform configurations from the root project to resolve NodeJsRootPlugin conflicts. Adjusted `.dockerignore` to allow pre-built artifacts and increased Gradle/Kotlin daemon memory for faster builds. Updated Caddyfile for runtime stability and added documentation for new build processes.

config/docker/caddy/web-app/Dockerfile

@@ -1,69 +1,16 @@
 # syntax=docker/dockerfile:1.8
 # ===================================================================
-# Multi-Stage Dockerfile for Meldestelle Web-App (Kotlin/JS)
-# Version: 3.0.0 - Caddy Edition with Runtime Config
+# Dockerfile for Meldestelle Web-App (Pre-built Artifacts)
+# Version: 3.1.0 - Local Build Injection
 # ===================================================================
 
 # === GLOBAL ARGS ===
-ARG GRADLE_VERSION=9.3.1
-ARG JAVA_VERSION=25
 ARG CADDY_VERSION=2.11-alpine
 ARG VERSION=1.0.0-SNAPSHOT
 ARG BUILD_DATE
 
 # ===================================================================
-# Stage 1: Build Stage
-# ===================================================================
-FROM gradle:${GRADLE_VERSION}-jdk${JAVA_VERSION} AS builder
-
-LABEL stage=builder
-WORKDIR /workspace
-
-# 1. Gradle Optimizations (Memory & Caching)
-# Increased Heap to 4g for Kotlin 2.3 JS Compilation
-# REMOVED: -Dorg.gradle.daemon=false (We want the daemon to handle classloading correctly!)
-ENV GRADLE_OPTS="-Dorg.gradle.caching=true \
-                 -Dorg.gradle.parallel=true \
-                 -Dorg.gradle.workers.max=4 \
-                 -Dorg.gradle.jvmargs=-Xmx4g \
-                 -XX:+UseParallelGC"
-ENV GRADLE_USER_HOME=/home/gradle/.gradle
-
-# 2. Dependency Layering (Optimize Cache Hit Rate)
-COPY gradlew gradlew.bat gradle.properties settings.gradle.kts ./
-COPY gradle/ gradle/
-# Copy Version Catalog explicitly first!
-COPY gradle/libs.versions.toml gradle/libs.versions.toml
-
-RUN chmod +x gradlew
-
-# 3. Copy Sources (Monorepo Structure)
-COPY platform/ platform/
-COPY core/ core/
-COPY backend/ backend/
-COPY frontend/ frontend/
-COPY config/ config/
-COPY contracts/ contracts/
-
-# Create dummy docs dir
-RUN mkdir -p docs
-
-# 4. Build Web App
-# REMOVED: --no-daemon flag to allow Gradle to manage its classloaders properly
-# This fixes the "IsolatedKotlinClasspathClassCastException" in Gradle 9.x + KMP
-RUN --mount=type=cache,target=/home/gradle/.gradle/caches \
-    --mount=type=cache,target=/home/gradle/.gradle/wrapper \
-    ./gradlew :frontend:shells:meldestelle-portal:jsBrowserDistribution \
-    -Pproduction=true \
-    -PnoSourceMaps=true \
-    --stacktrace
-
-# 5. Prepare Dist
-RUN mkdir -p /app/dist && \
-    cp -r frontend/shells/meldestelle-portal/build/dist/js/productionExecutable/* /app/dist/
-
-# ===================================================================
-# Stage 2: Runtime Stage (Caddy)
+# Stage 1: Runtime Stage (Caddy)
 # ===================================================================
 FROM caddy:${CADDY_VERSION}
 
@@ -79,11 +26,12 @@ LABEL service="web-app" \
 COPY config/docker/caddy/web-app/Caddyfile /etc/caddy/Caddyfile
 COPY config/docker/caddy/web-app/config.json /usr/share/caddy/config.json
 
-# Copy Static Assets from Builder
-COPY --from=builder /app/dist/ /usr/share/caddy/
+# Copy Pre-built Static Assets from Host
+# NOTE: You must run `./gradlew :frontend:shells:meldestelle-portal:jsBrowserDistribution -Pproduction=true` locally first!
+COPY frontend/shells/meldestelle-portal/build/dist/js/productionExecutable/ /usr/share/caddy/
 
 # Ensure favicon exists (fallback)
-COPY --from=builder /workspace/config/docker/nginx/web-app/favicon.svg /usr/share/caddy/favicon.svg
+COPY config/docker/nginx/web-app/favicon.svg /usr/share/caddy/favicon.svg
 
 EXPOSE 4000