feat: ship Peptide Reconstitution Calculator v1.0.0

Interactive reconstitution calculator with peptide-specific presets.

Core features:
- [prc_calculator] shortcode with instant client-side math
- Concentration (mg/mL), mcg/unit, injection volume, syringe units, doses/vial
- Live presets from PR Core dosing data (graceful fallback to 8 defaults)
- REST API (prc/v1): presets list/detail + server-side calculate
- Transient-cached presets with event-driven invalidation
- Dark mode + responsive design (320px+)
- Full teardown in uninstall.php

12 PHP files (max 241 lines), 1 JS file, 1 CSS file.
CI: PHP lint 8.1-8.3, PHPCS WordPress, 300-line check.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -0,0 +1,21 @@
+# Changelog
+
+All notable changes to Peptide Reconstitution Calculator are documented here.
+Format: [Semantic Versioning](https://semver.org/).
+
+## [1.0.0] — 2026-04-17
+
+### Added
+- Interactive reconstitution calculator via `[prc_calculator]` shortcode.
+- Client-side instant calculation: concentration (mg/mL), mcg per syringe unit, injection volume (mL), syringe units (IU), doses per vial.
+- Peptide-specific presets from Peptide Repo Core (when active) with live dosing data.
+- 8 built-in default presets: BPC-157, TB-500, Semaglutide, CJC-1295 (DAC), Ipamorelin, PT-141, MK-677, GHRP-6.
+- Preset pre-selection via shortcode attribute: `[prc_calculator peptide="bpc-157"]`.
+- REST API (`prc/v1`): GET /presets, GET /presets/{slug}, POST /calculate.
+- Server-side math engine (`PRC_Math`) mirroring client-side calculations.
+- Transient-cached presets with event-driven invalidation on PR Core data changes.
+- Admin notice when PR Core is not installed (informational, not blocking).
+- Dark mode support via `prefers-color-scheme`.
+- Responsive design down to 320px viewport.
+- Full teardown in `uninstall.php` (options + transients).
+- CI workflow: PHP lint (8.1/8.2/8.3), PHPCS WordPress, 300-line file check.