feat(v1.4.0): CSV/Excel/JSON/NextUp exports + hybrid smart year standing

- Export modules (export-csv/json/xlsx) mirroring the PDF layout, plus a
  Next Up import CSV matching the raycast/nextup column contract.
- Hybrid Year Level: View Grades history (exact per-semester standing),
  falling back to units math (prospectus total - lacking), then profile.
  Popup adds a year-mode setting (auto/custom/off).
- On-page button row now offers PDF / CSV / Excel / JSON / Next Up.
- Bump version to 1.4.0.
- Tag-only build workflow with an optional AMO sign step for a signed .xpi;
  separate ci.yml keeps tests on pushes/PRs.
- Tests: year-standing parser tests + export tests (CSV quoting, JSON schema,
  XLSX structure); CI validates XLSX via openpyxl.

README.md

@@ -84,12 +84,24 @@ built `ismis-helper-chrome.zip` directly:
 
 - **Saved login profiles** (stored in `browser.storage.local`) — only one enabled at
   a time, with a master on/off toggle.
-- **One-click Download PDF** button on the Study Load page.
+- **One-click Download PDF** button on the Study Load page, plus **CSV / Excel /
+  JSON / Next Up** export buttons.
 - PDF settings in the popup:
   - Truncate long course descriptions to match the official PDF (default on).
   - Show/hide `Year Level`, and set a custom Year Level value.
+  - Year Level mode: `Auto` (recommended), `Use custom value`, or `Profile value
+    only`.
+- **Smart Year Level**: for the semester being printed, `Auto` derives the
+  standing from the View Grades history (exact) or, failing that, from remaining
+  units (Student Prospectus total − Lacking Subjects). Custom value overrides;
+  the profile-scraped value is the fallback.
+- **Next Up import**: the Next Up export writes CSV in the exact column contract
+  the Raycast [Next Up](https://github.com/) extension accepts
+  (`title, courseCode, days, startTime, endTime, room, units, professorName`),
+  so schedules drop straight into the app.
 - **Bundled Segoe UI fonts** for a 1:1 look with the official document.
-- Builds and packages automatically via Gitea Actions (zips + versioned releases).
+- Builds and packages automatically via Gitea Actions (zips + versioned releases
+  with a signed `.xpi`).
 
 ## Build
 
@@ -114,7 +126,11 @@ additionally creates a **Gitea Release** with both versioned zips attached.
 Open the extension popup to:
 - Manage login profiles (add / edit / enable).
 - Toggle the master on/off switch.
-- Set PDF options: truncate descriptions, show/hide `Year Level`, custom Year Level.
+- Set PDF options: truncate descriptions, show/hide `Year Level`, Year Level
+  mode, and a custom Year Level value.
+
+The Study Load page gets a button row — **Download PDF**, **CSV**, **Excel**,
+**JSON**, and **Next Up** — next to the total-units line.
 
 ## Data & privacy