Fix initial page rendering

[vladiant]

Summary

Fixes Internal Server Error on Render when loading / and makes homepage template loading robust across source and packaged deployments.

This MR also updates packaging so the styled homepage template is always included in built artifacts (wheel/sdist), and keeps a single template source of truth at app/templates/index.html.

Problem

The root page (/) could fail in hosted environments (Render) with TemplateNotFound, causing HTTP 500.

Root Cause

Template path resolution was tied to repository layout assumptions. In packaged/runtime environments, template files may live under installed package paths, not the repo root.

What Changed

1. Resilient template directory resolution

• Added _resolve_template_directories() in app/main.py to search multiple locations:
  • <repo>/templates
  • <site-packages>/app/templates
  • <cwd>/templates
• Jinja2Templates now uses discovered existing directories.

2. Safe fallback for missing template

• Wrapped root-page template rendering in try/except TemplateNotFound.
• If template is unavailable, return a minimal HTML page with links to:
  • /docs
  • /redoc
  • /health
• Prevents 500 on / in degraded template scenarios.

3. Packaging fixes for template inclusion

• Updated pyproject.toml:
  • include-package-data = true
  • package discovery via [tool.setuptools.packages.find] include = ["app*"]
  • package data rule: app = ["templates/*.html"]
• Ensures app/templates/index.html is included in wheel/sdist.

4. Single source of truth for homepage template

• Moved template from templates/index.html to app/templates/index.html.
• Removed duplicate root template file.

5. Regression test coverage

• Added test to verify / still returns 200 when template loading raises TemplateNotFound.
• Keeps behavior protected against future regressions.

Files Changed

• app/main.py
• pyproject.toml
• app/templates/index.html (moved from templates/index.html)
• tests/test_api.py

Validation

Executed targeted tests:

• tests/test_api.py::test_home_page_endpoint
• tests/test_api.py::test_home_page_endpoint_falls_back_when_template_missing

Result: both passed.

Also validated package artifact contents during development:

• app/templates/index.html present in built wheel/sdist.
• app subpackages included correctly via package discovery.

Impact

• No API contract changes.
• Improves deployment reliability for Render and other packaged environments.
• Root endpoint degrades gracefully instead of failing with 500 when template files are missing.

Rollback Plan

• Revert this MR to restore previous template loading behavior and packaging config.
• No data migration or schema rollback required.