docs(06-01): complete mentor notification opt-in plan

Tasks completed: 2/2
- User preferences class with notification opt-in meta
- Helper method to query opted-in mentors

SUMMARY: .planning/phases/06-email-notifications/06-01-SUMMARY.md

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

.planning/ROADMAP.md

@@ -112,5 +112,5 @@ Plans:
 | 3. Job Management Core | 4/4 | Complete | 2026-01-14 |
 | 4. Job Deactivation System | 2/2 | Complete | 2026-01-14 |
 | 5. Mentor Job Board | 4/4 | Complete | 2026-01-14 |
-| 6. Email Notifications | 0/3 | Not started | - |
+| 6. Email Notifications | 2/3 | In progress | - |
 | 7. Testing & Polish | 0/3 | Not started | - |

.planning/STATE.md

@@ -12,7 +12,7 @@ See: .planning/PROJECT.md (updated 2026-01-14)
 Phase: 6 of 7 (Email Notifications)
 Plan: 2 of 3 in current phase
 Status: In progress
-Last activity: 2026-01-14 — Completed Plan 06-02 (Action Scheduler integration)
+Last activity: 2026-01-14 — Documented Plan 06-01 (Mentor notification opt-in)
 
 Progress: ████████████░ 64%
 

.planning/phases/06-email-notifications/06-01-SUMMARY.md

@@ -0,0 +1,68 @@
+---
+phase: 06-email-notifications
+plan: 01
+subsystem: user-management
+tags: [user-preferences, notifications, opt-in, user-meta]
+requires: [03-03]
+provides: [mentor-notification-opt-in-system, opted-in-mentors-query]
+affects: [06-03]
+tech-stack:
+  added: []
+  patterns: [user-meta-preferences, profile-hooks]
+key-files:
+  created: [includes/class-user-preferences.php]
+  modified: [includes/class-ddhh-job-manager.php, ddhh-job-manager.php]
+key-decisions: []
+issues-created: []
+duration: 3 min
+completed: 2026-01-14
+---
+
+# Phase 6 Plan 1: Mentor Notification Opt-In Summary
+
+**Mentor notification preference system with profile UI toggle and query helper for opted-in users**
+
+## Accomplishments
+
+- Created DDHH_JM_User_Preferences class following singleton pattern
+- Added notification opt-in checkbox on subscriber user profiles (German labels)
+- Implemented user meta field 'ddhh_jm_notify_new_jobs' with secure save handling
+- Built get_opted_in_mentors() helper method for efficient user ID queries
+- Integrated class initialization into main plugin workflow
+
+## Files Created/Modified
+
+- `includes/class-user-preferences.php` - User preferences class with profile UI and query methods
+- `includes/class-ddhh-job-manager.php` - Added initialization of user preferences hooks
+- `ddhh-job-manager.php` - Added require statement for user preferences class
+
+## Implementation Details
+
+**Task 1: User Preferences Class**
+- Class structure: Static methods with setup_hooks() pattern
+- Profile display hooks: show_user_profile and edit_user_profile (covers own profile and admin edit)
+- Role filtering: Only shows for users with 'subscriber' role (mentors)
+- UI label: "Benachrichtigungen über neue Stellenangebote erhalten" (German)
+- Help text: "Sie erhalten eine E-Mail, wenn ein neues Stellenangebot veröffentlicht wird."
+- Security: Nonce verification for all save operations
+- Meta key: 'ddhh_jm_notify_new_jobs' (boolean: '1' = opted in, '0' or missing = opted out)
+- Default behavior: Opt-out (users must explicitly enable)
+
+**Task 2: Query Helper Method**
+- Method: get_opted_in_mentors() returns array of user IDs
+- Query: WP_User_Query with role='subscriber' and meta_query for opt-in value
+- Optimization: fields='ID' returns only IDs (efficient for batch processing)
+- Error handling: Logs to error_log if query fails, returns empty array
+- Ready for Phase 06-03 email batch processing
+
+## Decisions Made
+
+None - implementation followed established patterns and plan specifications exactly.
+
+## Issues Encountered
+
+None - straightforward implementation using WordPress user meta and profile hooks.
+
+## Next Step
+
+Ready for Plan 06-03 (async email batch processing on job publish). Plan 06-02 (Action Scheduler integration) is already complete and provides the async infrastructure needed.