Add floating canvas panels, theme settings, and SVG line-spacing analysis.

Canvas Studio now uses dockable floating panels, app settings/help navigation, and improved SVG export; the backend adds an SVG line-spacing analysis API with SciPy acceleration and new design templates.

backend/service/app.py

@@ -8,6 +8,7 @@ import re
 import shutil
 import sqlite3
 import threading
+import time
 import uuid
 from datetime import datetime, timezone
 from pathlib import Path
@@ -21,6 +22,7 @@ from PIL import Image, ImageDraw, ImageFont
 from core import config as wc_config
 from core.fonts import get_cached_font
 from .job_manager import JobManager
+from .line_spacing import analyze_svg_line_spacing_file
 from .log_config import get_logger
 from .runner import JobRunner
 from .schemas import (
@@ -32,6 +34,8 @@ from .schemas import (
     JobLocationSearchResult,
     JobResult,
     JobStatus,
+    LineSpacingAnalysisRequest,
+    LineSpacingAnalysisSummary,
     Project,
     ProjectSummary,
     Template,
@@ -973,6 +977,45 @@ def download_asset(asset_id: str):
     return FileResponse(path, media_type=media, filename=f"{meta['name']}{ext}")
 
 
+@app.post("/api/assets/{asset_id}/line-spacing", response_model=LineSpacingAnalysisSummary)
+def analyze_asset_line_spacing(
+    asset_id: str,
+    request: LineSpacingAnalysisRequest,
+) -> LineSpacingAnalysisSummary:
+    d = _asset_dir(asset_id)
+    meta = _read_asset_meta(d)
+    if not meta:
+        raise HTTPException(status_code=404, detail="asset not found")
+    if meta.get("mime_type") != "image/svg+xml":
+        raise HTTPException(status_code=400, detail="line spacing analysis only supports SVG assets")
+
+    path = d / "asset.svg"
+    if not path.exists():
+        raise HTTPException(status_code=404, detail="asset file missing on disk")
+
+    started = time.perf_counter()
+    try:
+        result = analyze_svg_line_spacing_file(
+            path,
+            percentile=request.percentile,
+            element_width=request.elementWidth,
+            element_height=request.elementHeight,
+            sample_step=request.sampleStep,
+        )
+    except ValueError as exc:
+        raise HTTPException(status_code=400, detail=str(exc)) from exc
+    elapsed = time.perf_counter() - started
+    log.info(
+        "[API] line-spacing asset=%s percentile=%s curves=%s segments=%s elapsed=%.2fs",
+        asset_id,
+        result.percentile,
+        result.curveCount,
+        result.segmentCount,
+        elapsed,
+    )
+    return LineSpacingAnalysisSummary(**result.as_dict())
+
+
 @app.delete("/api/assets/{asset_id}", status_code=204)
 def delete_asset(asset_id: str) -> None:
     d = _asset_dir(asset_id)