docs: add CHANGELOG.md and update README version to 1.6.0

- CHANGELOG.md: full history from 1.0.0 → 1.6.0 (Keep a Changelog format)
- README.md: bump version badge 1.5.0 → 1.6.0, add changelog summary table

CHANGELOG.md

@@ -0,0 +1,77 @@
+# Changelog
+
+All notable changes to the Eventify Backend are documented here.
+Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), versioning follows [Semantic Versioning](https://semver.org/).
+
+---
+
+## [1.6.0] — 2026-04-02
+
+### Added
+- **Unique Eventify ID system** (`EVT-XXXXXXXX` format)
+  - New `eventify_id` field on `User` model — `CharField(max_length=12, unique=True, editable=False, db_index=True)`
+  - Charset `ABCDEFGHJKLMNPQRSTUVWXYZ23456789` (no ambiguous characters I/O/0/1) giving ~1.78T combinations
+  - Auto-generated on first `save()` via a 10-attempt retry loop using `secrets.choice()`
+  - Migration `0012_user_eventify_id`: add nullable → backfill all existing users → make non-null
+- `eventify_id` exposed in `accounts/api.py` → `_partner_user_to_dict()` fields list
+- `eventify_id` exposed in `partner/api.py` → `_user_to_dict()` fields list
+- `eventify_id` exposed in `mobile_api/views/user.py` → `LoginView` response (populates `localStorage.event_user.eventify_id`)
+- `eventifyId` exposed in `admin_api/views.py` → `_serialize_user()` (camelCase for direct TypeScript compatibility)
+- Server-side search in `UserListView` now also filters on `eventify_id__icontains`
+- Synced migration `0011_user_allowed_modules_alter_user_id` (pulled from server, was missing from local repo)
+
+### Changed
+- `accounts/models.py`: merged `allowed_modules` field + `get_allowed_modules()` + `ALL_MODULES` constant from server (previously only existed on server)
+
+---
+
+## [1.5.0] — 2026-03-31
+
+### Added
+- `allowed_modules` TextField on `User` model — comma-separated module slug access control
+- `get_allowed_modules()` method on `User` — returns list of accessible modules based on role or explicit list
+- `ALL_MODULES` class constant listing all platform module slugs
+- Migration `0011_user_allowed_modules_alter_user_id`
+
+---
+
+## [1.4.0] — 2026-03-24
+
+### Added
+- Partner portal login/logout APIs (`accounts/api.py`) — `PartnerLoginAPI`, `PartnerLogoutAPI`, `PartnerMeAPI`
+- `_partner_user_to_dict()` serializer for partner-scoped user data
+- Partner CRUD, KYC review, and user management endpoints in `partner/api.py`
+
+---
+
+## [1.3.0] — 2026-03-14
+
+### Changed
+- User `id` field changed from `AutoField` to `BigAutoField` (migration `0010_alter_user_id`)
+
+---
+
+## [1.2.0] — 2026-03-10
+
+### Added
+- `partner` ForeignKey on `User` model linking users to partners (migration `0009_user_partner`)
+- Profile picture upload support (`ImageField`) with `default.png` fallback (migration `0006–0007`)
+
+---
+
+## [1.1.0] — 2026-02-28
+
+### Added
+- Location fields on `User`: `pincode`, `district`, `state`, `country`, `place`, `latitude`, `longitude`
+- Custom `UserManager` for programmatic user creation
+
+---
+
+## [1.0.0] — 2026-03-01
+
+### Added
+- Initial Django project with custom `User` model extending `AbstractUser`
+- Role choices: `admin`, `manager`, `staff`, `customer`, `partner`, `partner_manager`, `partner_staff`, `partner_customer`
+- JWT authentication via `djangorestframework-simplejwt`
+- Admin API foundation: auth, dashboard metrics, partners, users, events
+- Docker + Gunicorn + PostgreSQL 16 production setup