[REFACTOR]: Store pre-loaded fillable PDFs in src/templates/ and outputs in src/outputs/

[utkarshqz]

📝 Description

Currently, FireForm requires users to upload a PDF via the API every session before they can fill any form. There is no persistent template storage — PDFs are saved to arbitrary paths and referenced by absolute path in the database.

This is a significant usability gap. In real operational use, a fire department uses the same 2–3 PDF templates repeatedly. Requiring re-upload every time creates unnecessary friction and is the root cause of the stale path bug.

💡 Rationale

Introducing a structured directory convention solves multiple problems simultaneously:

• Eliminates repeated PDF uploads for known agency templates
• Enables batch multi-template filling — one transcript can fill Police, Fire, and Ambulance PDFs simultaneously
• Fixes stale absolute path bug — relative paths from project root are stable across machines
• Enables department profile system — profiles map departments to their pre-loaded templates
• Onboarding — gives new contributors a clear, documented place to add their own fillable PDFs

🛠️ Proposed Solution

Introduce the following directory structure:

src/
  templates/          ← pre-stored fillable PDF templates
    fire_dept.pdf
    ambulance.pdf
    police.pdf
  outputs/            ← generated filled PDFs (gitignored)
    fire_dept_john_smith_2026-03-12.pdf
    ambulance_john_smith_2026-03-12.pdf

API changes:

• POST /templates/register — registers a PDF already present in src/templates/ by filename, no upload required
• POST /templates/upload — existing endpoint preserved for backwards compatibility
• Template DB records store relative path: src/templates/fire_dept.pdf

Documentation changes:

• SETUP.md — new section: "Adding your own PDF templates"
• README.md — updated project structure diagram

✅ Acceptance Criteria

• src/templates/ directory created with at least one sample fillable PDF
• src/outputs/ directory created with .gitkeep and added to .gitignore
• POST /templates/register endpoint added
• Template DB records use relative paths
• SETUP.md documents how to add templates for new contributors
• Batch filling ([FEAT]: Missing Batch Endpoint for Multi-Form Filing #156) can reference templates by filename without upload

📌 Additional Context

• Prerequisite for properly implementing batch multi-template filling ([FEAT]: Missing Batch Endpoint for Multi-Form Filing #156)
• Resolves stale path bug described in Issue ([BUG]: Stale template records cause 500 errors after re-clone or file move #235 )
• Aligns with department profile system ([FEAT]: Department Profile System for Pre-Mapped PDF Templates #206)
• No breaking changes — existing upload flow preserved