feat: per-task image/annotations, annotation editor toolbar, Tailwind compiled

- Add per-task file upload with image preview in task editor
- Add dedicated annotation editor page (task_drawing.html) with Fabric.js
- Add color picker, stroke width, and line dash controls to annotation toolbar
- Apply property changes to selected objects in real-time
- Disable style controls until a drawing tool or object is selected
- Remove zoom/pan from annotation toolbar (simplified UX)
- Auto-switch to select mode after placing annotation elements
- Show annotation overlay on task image previews (read-only canvas)
- Add file proxy route in measure blueprint for task file access
- Add file_path/file_type fields to TaskCreate/TaskUpdate Pydantic schemas
- Replace Tailwind CDN with compiled CSS (tailwind.config.js with full shades)
- Fix Alpine.js x-init crash: extract annotations JSON to <script> tags
  (recipe_preview.html, task_execute.html) to avoid HTML attribute breakage

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/blueprints/measure.py

@@ -1,11 +1,14 @@
 """MeasurementTec blueprint - recipe selection and measurement execution."""
+import requests as http_requests
+
 from flask import (
-    Blueprint, flash, jsonify, redirect, render_template,
+    Blueprint, Response, flash, jsonify, redirect, render_template,
     request, session, url_for,
 )
 from flask_babel import gettext as _
 
 from blueprints.auth import login_required, role_required
+from config import Config
 from services.api_client import api_client
 
 measure_bp = Blueprint("measure", __name__)
@@ -272,3 +275,25 @@ def save_measurement():
         }), status_code if status_code >= 400 else 500
 
     return jsonify(resp), 201
+
+
+# ---------------------------------------------------------------------------
+# Route: File proxy (browser can't send X-API-Key directly)
+# ---------------------------------------------------------------------------
+@measure_bp.route("/api/files/<path:file_path>", methods=["GET"])
+@login_required
+def api_get_file(file_path: str):
+    """Proxy: Serve file from API server (browser can't send X-API-Key)."""
+    api_key = session.get("api_key", "")
+    base_url = Config.API_SERVER_URL.rstrip("/")
+    resp = http_requests.get(
+        f"{base_url}/api/files/{file_path}",
+        headers={"X-API-Key": api_key},
+        timeout=30,
+    )
+    if resp.status_code != 200:
+        return Response(resp.text, status=resp.status_code)
+    return Response(
+        resp.content,
+        content_type=resp.headers.get("content-type", "application/octet-stream"),
+    )