ci: run all checks and tests directly inside container build and push immediately

Dockerfile

@@ -1,29 +1,47 @@
 # ==============================================================================
-# Stage 1: Frontend Build (Runs natively on $BUILDPLATFORM — zero QEMU overhead)
+# Stage 1: Frontend Check & Build (Cached npm dependencies layer)
 # ==============================================================================
-FROM --platform=$BUILDPLATFORM node:22-alpine AS frontend-builder
+FROM node:22-alpine AS frontend-builder
 WORKDIR /app/frontend
 COPY frontend/package*.json ./
 RUN npm install --no-audit --no-fund
 COPY frontend/ ./
-RUN npm run build
+RUN npx tsc --noEmit && npm run build
 
 # ==============================================================================
-# Stage 2: Go Backend Build (Native Cross-Compile via TARGETOS / TARGETARCH)
+# Stage 2: Go Backend Lint, Unit Tests & Binary Build (Cached Go module & sqlite layer)
 # ==============================================================================
-FROM --platform=$BUILDPLATFORM golang:1.23-alpine AS backend-builder
-ARG TARGETOS=linux
-ARG TARGETARCH=amd64
+FROM golang:1.23-alpine AS backend-builder
 WORKDIR /app
 RUN apk add --no-cache git ca-certificates
+
+# Cache Go modules & pre-compile heavy dependencies (modernc.org/sqlite) in a dedicated layer
 COPY go.mod ./
+RUN go get github.com/go-chi/chi/v5@v5.2.0 \
+    github.com/go-chi/cors@v1.2.1 \
+    github.com/golang-jwt/jwt/v5@v5.2.1 \
+    github.com/gorilla/websocket@v1.5.3 \
+    golang.org/x/crypto/bcrypt@v0.31.0 \
+    modernc.org/sqlite@v1.34.4 && \
+    CGO_ENABLED=0 go build \
+      modernc.org/sqlite \
+      github.com/go-chi/chi/v5 \
+      github.com/go-chi/cors \
+      github.com/golang-jwt/jwt/v5 \
+      github.com/gorilla/websocket \
+      golang.org/x/crypto/bcrypt
+
+# Copy application source & compiled frontend SPA assets for go:embed
 COPY cmd/ ./cmd/
 COPY internal/ ./internal/
 COPY migrations/ ./migrations/
-# Copy compiled frontend SPA assets into cmd/server/dist for go:embed
 COPY --from=frontend-builder /app/frontend/dist ./cmd/server/dist
-RUN go mod tidy
-RUN CGO_ENABLED=0 GOOS=${TARGETOS} GOARCH=${TARGETARCH} go build -ldflags="-s -w" -o /app/mindsift ./cmd/server
+
+# Run go mod tidy, static analysis (go vet), unit tests (go test), and compile final binary
+RUN go mod tidy && \
+    CGO_ENABLED=0 go vet ./... && \
+    CGO_ENABLED=0 go test -v ./... && \
+    CGO_ENABLED=0 go build -ldflags="-s -w" -o /app/mindsift ./cmd/server
 
 # ==============================================================================
 # Stage 3: Minimal Production Runtime (< 35 MB)