feat: add latex_serif export template and fonts

[Sathvik-Rao]

Introduce a new "latex_serif" (LaTeX-style serif) export template across the app. Update README and allowed template set; add full generator support for DOCX and ODT formats including layout code to match the PDF LaTeX look. Bundle CMU Serif and Font Awesome TTFs plus license files, implement DOCX OOXML font obfuscation/embedding and ODT handling (with icon rasterization fallback), and add layout helpers (small-caps name, hfill rows, itemized bullets, etc.). Update tests and front-end bits to surface the new template; DOCX embedding falls back to font-name-only if embedding fails. Include sidebar resize and improved diff UI.

Summary

Type of change

• fix: ... — bug fix → patch bump (0.0.x)
• feat: ... — new feature → minor bump (0.x.0)
• feat!: ... / BREAKING CHANGE — breaking change → major bump (x.0.0)
• chore: / docs: / ci: / refactor: — no release created

PR title format

Your PR title becomes the commit message on merge and determines the version bump:

feat(resume): add cover letter section
fix: pdf export crash on empty work history
feat!: replace /generate endpoint with /build (breaking)
chore: update dev dependencies

Pattern: type(optional-scope): short description in lowercase

Checklist

• Tests added / updated under backend/tests/ for any changed backend/app/ code
• pytest passes locally (cd backend && pytest)
• PR title follows the format above

[github-actions]

Suggested tests for this PR

PR title: feat: add latex_serif export template and fonts

PR description:

Introduce a new "latex_serif" (LaTeX-style serif) export template across the app. Update README and allowed template set; add full generator support for DOCX and ODT formats including layout code to match the PDF LaTeX look. Bundle CMU Serif and Font Awesome TTFs plus license files, implement DOCX OOXML font obfuscation/embedding and ODT handling (with icon rasterization fallback), and add layout helpers (small-caps name, hfill rows, itemized bullets, etc.). Update tests and front-end bits to surface the new template; DOCX embedding falls back to font-name-only if embedding fails. Include sidebar resize and improved diff UI.

Summary

Type of change

• fix: ... — bug fix → patch bump (0.0.x)
• feat: ... — new feature → minor bump (0.x.0)
• feat!: ... / BREAKING CHANGE — breaking change → major bump (x.0.0)
• chore: / docs: / ci: / refactor: — no release created

PR title format

Your PR title becomes the commit message on merge and determines the version bump:

feat(resume): add cover letter section
fix: pdf export crash on empty work history
feat!: replace /generate endpoint with /build (breaking)
chore: update dev dependencies

Pattern: type(optional-scope): short description in lowercase

Checklist

• Tests added / updated under backend/tests/ for any changed backend/app/ code
• pytest passes locally (cd backend && pytest)
• PR title follows the format above

Based on the title, description, and changed files below, please make sure the PR includes tests that:

• Cover the behaviour described in "feat: add latex_serif export template and fonts".
• Exercise the happy path and at least one failure / edge case.
• Live under backend/tests/ mirroring the changed module path.

Changed backend code files:

• backend/app/api/document_routes.py
• backend/app/documents/docx_generator.py
• backend/app/documents/odt_generator.py
• backend/app/documents/pdf_generator.py
• backend/app/schemas.py

These modules changed but do not appear to have matching test updates — please add tests:

• backend/app/api/document_routes.py
• backend/app/documents/docx_generator.py
• backend/app/documents/odt_generator.py
• backend/app/documents/pdf_generator.py
• backend/app/schemas.py