feat: add web layer (internal/web) and wire it into main.go

Routing, html/template layout/content pattern, and the Pre-Publish
check flow: POST /pruefen runs extraction (Stufe 1) then rules.Evaluate
(Stufe 2) and renders the result as an htmx fragment. Nothing is
persisted yet — that's the next step (wiring internal/store in).

The needsClarification case is rendered explicitly as a request for
more information rather than "no findings", matching the core
principle. Every result carries the legal-advice disclaimer required by
CLAUDE.md's guardrails.

Server depends on a narrow Extractor interface rather than *extract.
Client directly, so tests inject a fake instead of calling the real API
— internal/web's test suite never touches the network. htmx is vendored
locally (internal/web/static/htmx.min.js) instead of loaded from a CDN,
keeping the UI usable without runtime internet access.

cmd/deklarix/main.go now wires all of this together: reads
ANTHROPIC_API_KEY (required) and RULES_DIR (default "rules"), builds
the extract client and loads the rule set, and serves web.Server instead
of the old inline health-only mux.

This exposed the same crash-loop risk fixed earlier for DATABASE_URL:
postinst's start guard only checked DATABASE_URL, so a fresh install
would now crash-loop on a missing ANTHROPIC_API_KEY instead. The guard
checks both. scripts/build.sh also now ships rules/*.yaml into the .deb
under /usr/share/deklarix/rules (not a conffile — rules are updated via
the release pipeline, never hand-edited on a server), and
deklarix.env.example points RULES_DIR there by default.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

scripts/build.sh

@@ -44,6 +44,7 @@ for ARCH in "${ARCHS[@]}"; do
     log "Baue Binary ($ARCH)..."
     mkdir -p "$DEB_DIR/DEBIAN" \
              "$DEB_DIR/usr/bin" \
+             "$DEB_DIR/usr/share/deklarix/rules" \
              "$DEB_DIR/etc/systemd/system" \
              "$DEB_DIR/etc/deklarix"
     CGO_ENABLED=0 GOARCH=$ARCH GOOS=linux go build \
@@ -62,6 +63,7 @@ for ARCH in "${ARCHS[@]}"; do
 
     cp "$PACKAGING_DIR/etc/systemd/system/deklarix.service" "$DEB_DIR/etc/systemd/system/"
     cp "$PACKAGING_DIR/etc/deklarix/deklarix.env.example"   "$DEB_DIR/etc/deklarix/"
+    cp "$REPO_DIR"/rules/*.yaml "$DEB_DIR/usr/share/deklarix/rules/"
 
     dpkg-deb --build --root-owner-group "$DEB_DIR" "$REPO_DIR/dist/$DEB_NAME.deb"