• 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/environments/{environment}/feature-lifecycle-counts/

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

2. Adds new query params to the existing GET /api/v1/projects/{project_pk}/features/ (list):
   • lifecycle_stage: one of stages below; requires environment.
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:

How did you test this code?

• New tests
• Will gradually roll out in production and collect perf data
• LLM-assisted benchmarking (does not represent production):

method: synthetic data, InfluxDB analytics backend, local Docker (indicative)
baseline: main's list/detail query path (already annotates code-refs), no lifecycle

small_project:        # 1K flags, 200 in use
  influxdb_query: ~80ms
  feature_list:
    baseline_main: ~2ms
    pr_no_stage_filter: ~40ms
    pr_filtered_by_stage: ~85ms
  feature_detail:
    baseline_main: ~1ms
    pr_with_lifecycle: ~35ms
  stage_counts_endpoint: ~55ms   # new in PR, no baseline

stress_test:          # 30K flags, 600 in use — deliberate worst-case
  influxdb_query: ~120ms
  feature_list:
    baseline_main: ~8ms
    pr_no_stage_filter: ~0.12s
    pr_filtered_by_stage: ~0.45s
  feature_detail:
    baseline_main: ~1ms
    pr_with_lifecycle: ~70ms
  stage_counts_endpoint: ~0.35s

How to review

Reviewing is easier if you split:

• Part 1: InfluxDB API refactor (to enable tests) — it revealed we need to rewrite it, or maybe invest in something else.
• Part 2: Feature Lifecycle stage counts API (to feed the count badges in the sidebar.
• Part 3: Extend the feature list and retrieve endpoints with lifecycle stage information.
• Part 4: Add filter by lifecycle stage capability to the feature list endpoint.