fix: add missing deps, fix Union import, remove redundant DB query

[utkarshqz]

Description

Fixes four bugs discovered during local setup and end-to-end testing of the API.

A fresh pip install -r requirements.txt on a clean environment fails immediately because python-multipart (required by FastAPI for file uploads) and pypdf (imported in api/routes/templates.py) are missing from the dependency list. Additionally, api/main.py raises a NameError on startup due to a missing Union import, and POST /forms/fill makes a redundant database query on every request.

Fixes #204
Fixes #187
Fixes #135
Fixes #149
Fixes #145

Type of change

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Tested on Windows 11, Python 3.11, clean virtual environment.

1. Created fresh venv: python -m venv venv && venv\Scripts\activate
2. Ran pip install -r requirements.txt — all packages install without errors
3. Started server: uvicorn api.main:app --reload — no NameError on startup
4. Uploaded a PDF via POST /templates/create — succeeds (previously failed with python-multipart error)
5. Called POST /forms/fill — single DB query confirmed in SQLAlchemy logs

• Manual end-to-end test (upload → fill → verify)
• Existing unit tests pass locally

Test Configuration:

• OS: Windows 11
• Python: 3.11
• Ollama: 0.17.7 / Mistral 7B

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules