feat(Feature Lifecycle): Update API with feature lifecycle info

[emyller]

• I have read the Contributing Guide.
• I have added information to docs/ if required so people know about the feature.
• I have filled in the "Changes" section below.
• I have filled in the "How did you test this code" section below.

Changes

Closes #7433

1. Introduces a new endpoint (also to MCP) /api/v1/projects/{project_pk}/features/lifecycle-status-counts/?environment=42

   {
     "NEW": 475,
     "LIVE": 734,
     "PERMANENT": 190,
     "STALE": 374,
     "NEEDS_MONITORING": 30,
     "TO_REMOVE": 197
   }

2. Adds new query params on the existing GET /api/v1/projects/{project_pk}/features/ (list):
   • lifecycle_stage: one of stages below; requires environment.
   • evaluation_period_days:
     • A larger window means more caution, as fewer features classify as TO_REMOVE
     • A shorter window means more aggressive
3. Adds a new attribute lifecycle_stage to the above list endpoint, and also to .../{feature_id} (retrieve), also carrying one of stages below.

Stages logical propositions are as follows:

State	Condition
PERMANENT	has_permanent_tag
LIVE	~has_permanent_tag AND ~has_stale_tag AND has_code_references
NEW	~has_permanent_tag AND ~has_stale_tag AND ~has_code_references
STALE	~has_permanent_tag AND has_stale_tag AND has_code_references
NEEDS_MONITORING	~has_permanent_tag AND has_stale_tag AND ~has_code_references AND evaluated_recently
TO_REMOVE	~has_permanent_tag AND has_stale_tag AND ~has_code_references AND ~evaluated_recently

How did you test this code?

• New tests

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Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview, Comment	Jun 17, 2026 3:49am

2 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
flagsmith-frontend-preview	Ignored	Preview	Jun 17, 2026 3:49am
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[codecov]

Codecov Report

❌ Patch coverage is 99.11765% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.57%. Comparing base (e85f77b) to head (e75211b).

Files with missing lines	Patch %	Lines
api/app_analytics/analytics_db_service.py	83.33%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #7789    +/-   ##
========================================
  Coverage   98.57%   98.57%            
========================================
  Files        1464     1467     +3     
  Lines       56625    56959   +334     
========================================
+ Hits        55818    56149   +331     
- Misses        807      810     +3     

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