feat: v3.0 - canvas editor, JSON-only, no Excel, new UI

- Remove all Excel code (import, export, template, pandas, openpyxl)
- New canvas-based schedule editor with drag & drop (interact.js)
- Modern 3-panel UI: sidebar, canvas, documentation tab
- New data model: Block with id/date/start/end, ProgramType with id/name/color
- Clean API: GET /api/health, POST /api/validate, GET /api/sample, POST /api/generate-pdf
- Rewritten PDF generator using ScenarioDocument directly (no DataFrame)
- Professional PDF output: dark header, colored blocks, merged cells, legend, footer
- Sample JSON: "Zimní výjezd oddílu" with 11 blocks, 3 program types
- 30 tests passing (API, core models, PDF generation)

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

app/core/validator.py

@@ -1,18 +1,9 @@
-"""
-Validation logic for Scenar Creator.
-Extracted from scenar/core.py — validate_inputs, validate_excel_template, overlap detection.
-"""
+"""Validation logic for Scenar Creator v3."""
 
-import pandas as pd
-from datetime import datetime
 import logging
 
 logger = logging.getLogger(__name__)
 
-DEFAULT_COLOR = "#ffffff"
-MAX_FILE_SIZE_MB = 10
-REQUIRED_COLUMNS = ["Datum", "Zacatek", "Konec", "Program", "Typ", "Garant", "Poznamka"]
-
 
 class ScenarsError(Exception):
     """Base exception for Scenar Creator."""
@@ -22,48 +13,3 @@ class ScenarsError(Exception):
 class ValidationError(ScenarsError):
     """Raised when input validation fails."""
     pass
-
-
-class TemplateError(ScenarsError):
-    """Raised when Excel template is invalid."""
-    pass
-
-
-def validate_inputs(title: str, detail: str, file_size: int) -> None:
-    """Validate user inputs for security and sanity."""
-    if not title or not isinstance(title, str):
-        raise ValidationError("Title is required and must be a string")
-    if len(title.strip()) == 0:
-        raise ValidationError("Title cannot be empty")
-    if len(title) > 200:
-        raise ValidationError("Title is too long (max 200 characters)")
-
-    if not detail or not isinstance(detail, str):
-        raise ValidationError("Detail is required and must be a string")
-    if len(detail.strip()) == 0:
-        raise ValidationError("Detail cannot be empty")
-    if len(detail) > 500:
-        raise ValidationError("Detail is too long (max 500 characters)")
-
-    if file_size > MAX_FILE_SIZE_MB * 1024 * 1024:
-        raise ValidationError(f"File size exceeds {MAX_FILE_SIZE_MB} MB limit")
-
-
-def normalize_time(time_str: str):
-    """Parse time string in formats %H:%M or %H:%M:%S."""
-    for fmt in ('%H:%M', '%H:%M:%S'):
-        try:
-            return datetime.strptime(time_str, fmt).time()
-        except ValueError:
-            continue
-    return None
-
-
-def validate_excel_template(df: pd.DataFrame) -> None:
-    """Validate that Excel has required columns."""
-    missing_cols = set(REQUIRED_COLUMNS) - set(df.columns)
-    if missing_cols:
-        raise TemplateError(
-            f"Excel template missing required columns: {', '.join(missing_cols)}. "
-            f"Expected: {', '.join(REQUIRED_COLUMNS)}"
-        )