feat: master-resume workflows + global, persisted memory toggle

[Sathvik-Rao]

Summary

Master resumes

• "New from Master" split button: main side starts a chat from the default
  master verbatim (POST /api/sessions/from-master seeds it with no pipeline/
  LLM run, so it's guaranteed unchanged); caret picks any saved master.
• "Compare to Master" on every resume version diffs it against a chosen
  master (picker in the diff modal), reusing the existing diff engine.

Memory

• Make "Use memory" a global, backend-persisted preference
  (AppSettings.memory_enabled) instead of a per-chat reset; loaded on
  bootstrap, saved on toggle, survives chats/sessions/reloads.
• Each generated reply notes whether the master resume and/or profile
  memory were used, for later reference.

Fixes

• Contact location icon was Font Awesome location-pin (U+F041, a solid
  blob); switch to location-dot (U+F3C5) across PDF/DOCX/ODT exporters.
• Add the missing _MIGRATIONS entry for app_settings.memory_enabled —
  without it, existing SQLite DBs crashed on startup ("no such column").

Cleanup

• Reuse _resolve_default() in the from-master endpoint.
• Consolidate the two bootstrap /api/app-settings fetches into one.

Tests & docs

• Add cross-format contact-icon regression test, migration test, and
  settings/summary/message coverage for the memory feature (333 pass).
• README: document the master-resume workflows and global memory toggle.

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: master-resume workflows + global, persisted memory toggle

PR description:

Summary

Master resumes

• "New from Master" split button: main side starts a chat from the default
  master verbatim (POST /api/sessions/from-master seeds it with no pipeline/
  LLM run, so it's guaranteed unchanged); caret picks any saved master.
• "Compare to Master" on every resume version diffs it against a chosen
  master (picker in the diff modal), reusing the existing diff engine.

Memory

• Make "Use memory" a global, backend-persisted preference
  (AppSettings.memory_enabled) instead of a per-chat reset; loaded on
  bootstrap, saved on toggle, survives chats/sessions/reloads.
• Each generated reply notes whether the master resume and/or profile
  memory were used, for later reference.

Fixes

• Contact location icon was Font Awesome location-pin (U+F041, a solid
  blob); switch to location-dot (U+F3C5) across PDF/DOCX/ODT exporters.
• Add the missing _MIGRATIONS entry for app_settings.memory_enabled —
  without it, existing SQLite DBs crashed on startup ("no such column").

Cleanup

• Reuse _resolve_default() in the from-master endpoint.
• Consolidate the two bootstrap /api/app-settings fetches into one.

Tests & docs

• Add cross-format contact-icon regression test, migration test, and
  settings/summary/message coverage for the memory feature (333 pass).
• README: document the master-resume workflows and global memory toggle.

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: master-resume workflows + global, persisted memory toggle".
• 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/_pipeline.py
• backend/app/api/messages_routes.py
• backend/app/api/sessions_routes.py
• backend/app/api/settings_routes.py
• backend/app/config.py
• backend/app/database.py
• backend/app/documents/docx_generator.py
• backend/app/documents/odt_generator.py
• backend/app/documents/pdf_generator.py
• backend/app/models.py
• backend/app/runtime_settings.py
• backend/app/schemas.py

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

• backend/app/api/_pipeline.py
• backend/app/api/messages_routes.py
• backend/app/api/sessions_routes.py
• backend/app/api/settings_routes.py
• backend/app/config.py
• backend/app/database.py
• backend/app/documents/docx_generator.py
• backend/app/documents/odt_generator.py
• backend/app/documents/pdf_generator.py
• backend/app/models.py
• backend/app/runtime_settings.py
• backend/app/schemas.py