[Feature] Implement automatic time data import from PDF and Excel files

[PPeitsch]

Description

Implemented file import system to automatically parse and import time records from PDF and Excel files.

Changes

• Added dependencies: \pandas, \pdfplumber, \openpyxl.
• Updated Database Model: Added \observation\ column to \ScheduleEntry.
• Implemented Importer Service with Factory pattern (PDF and Excel support).
• Created \import_log\ blueprint with Upload, Preview, and Confirm routes.
• Added UI templates for upload and preview.

Testing

• Added unit tests for importers in \ ests/test_importers.py.
• Verified file upload and parsing manually (implicitly via development cycle).

Checklist

• Code formatted with black/isort
• Mypy checks passed
• Tests passed

[codecov]

Codecov Report

❌ Patch coverage is 44.44444% with 160 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
app/routes/import_log.py	27.52%	79 Missing ⚠️
app/services/importer/pdf_importer.py	13.75%	69 Missing ⚠️
app/services/importer/excel_importer.py	81.25%	12 Missing ⚠️

Files with missing lines	Coverage Δ
app/__init__.py	100.00% <100.00%> (ø)
app/models/models.py	100.00% <100.00%> (ø)
app/services/importer/factory.py	100.00% <100.00%> (ø)
app/services/importer/protocol.py	100.00% <100.00%> (ø)
app/services/importer/excel_importer.py	81.25% <81.25%> (ø)
app/services/importer/pdf_importer.py	13.75% <13.75%> (ø)
app/routes/import_log.py	27.52% <27.52%> (ø)

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