feat: add section heading icons to PDF templates (#3127)

* feat: add section heading icons to PDF templates

Add customizable Phosphor icons before section titles in PDF output.
Users can toggle visibility globally via a new "Hide section heading icons"
switch (independent of item-level icons) and customize individual section
icons through the builder sidebar icon picker.

- Add `icon` field to `baseSectionSchema` and `summarySchema`
- Add `hideSectionIcons` to `pageSchema` (defaults to true for backward compat)
- Implement `SectionHeadingIcon` component with heading font-size scaling
- Support "none" sentinel for per-section icon hiding
- Fallback to sensible defaults (briefcase, graduation-cap, etc.) for legacy data
- Add icon picker to builder sidebar sections and custom section dialogs

Closes #2632

* test: add unit tests for section heading icons

- Add tests for getResumeSectionIcon() covering built-in sections,
  summary, custom sections, "none" sentinel, and default fallbacks
- Add schema tests for baseSectionSchema icon field, summarySchema icon,
  and pageSchema hideSectionIcons default behavior

* refactor: minor updates to icon display

* Update apps/web/locales/es-ES.po

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

---------

Co-authored-by: Amruth Pillai <im.amruth@gmail.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

packages/pdf/src/section-title.test.ts

@@ -109,6 +109,7 @@ describe("getResumeSectionTitle", () => {
 					id: "ext-1",
 					type: "cover-letter" as const,
 					title: "My Cover Letter",
+					icon: "",
 					columns: 1,
 					hidden: false,
 					items: [],
@@ -126,6 +127,7 @@ describe("getResumeSectionTitle", () => {
 					id: "ext-1",
 					type: "cover-letter" as const,
 					title: "",
+					icon: "",
 					columns: 1,
 					hidden: false,
 					items: [],