feat: multi-issuer OIDC support with config consolidation

- Support multiple OAuth providers (core-api, tatlock-ui, tatlock)
- Changed oidc_issuer (string) to oidc_issuers (list)
- Per-issuer JWKS caching
- Validates token issuer against allowed list
- Consolidated config files (removed deprecated src/config.py, src/security.py)
- Updated imports to use src/shared/config and src/shared/security

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,22 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.10.7] - 2026-01-08
+
+### Added
+
+- **Multi-issuer OIDC support** - Accept tokens from multiple OAuth providers
+  - Changed `oidc_issuer` (string) to `oidc_issuers` (list)
+  - Each issuer has its own JWKS endpoint, now cached per-issuer
+  - Validates token issuer against allowed list before fetching JWKS
+  - Supports tokens from: `core-api`, `tatlock-ui`, `tatlock` OAuth applications
+  - Completes fix for environment endpoint user resolution
+
+### Removed
+
+- Deprecated `src/config.py` - consolidated to `src/shared/config.py`
+- Deprecated `src/security.py` - consolidated to `src/shared/security.py`
+
 ## [1.10.6] - 2026-01-08
 
 ### Fixed