fix: remove frozen flag definitions and centralise CRE_ALLOW_IMPORT gate

[shiwani42]

Closes #871
Closes #869

Summary

Removed frozen ENABLE_MYOPENCRE and GAP_ANALYSIS_OPTIMIZED definitions from config.py. Upstream has since removed all usages of both flags; the frozen definitions were dead code.

Introduces application/feature_flags.py with is_cre_import_allowed(), which reads os.getenv("CRE_ALLOW_IMPORT") fresh on every call using a TRUE_VALUES whitelist (1, true, yes) matching upstream gate semantics.

Also fixes a pre-existing inconsistency in the /rest/v1/config endpoint: it previously returned True only for "1", while the gate accepted "1", "true", and "yes". Both now use is_cre_import_allowed() so the frontend reflects the actual gate state.

Why

Upstream removed the usages of ENABLE_MYOPENCRE and GAP_ANALYSIS_OPTIMIZED from web_main.py and db.py, but left their frozen definitions in config.py as dead code. This PR cleans them up.

CRE_ALLOW_IMPORT had the same import-time risk and was duplicated inline across multiple call sites in web_main.py with slightly inconsistent semantics (the gate and the /rest/v1/config endpoint checked different value sets). Centralising into feature_flags.py gives it a single source of truth and prevents future drift.

Changes

• application/feature_flags.py (new) - is_cre_import_allowed() reads dynamically at call time
• application/config.py - removed dead frozen definitions of ENABLE_MYOPENCRE and GAP_ANALYSIS_OPTIMIZED
• application/web/web_main.py - use is_cre_import_allowed() at all CRE_ALLOW_IMPORT call sites; /rest/v1/config now reflects the actual gate state
• application/tests/gap_analysis_db_test.py - removed stale Config.GAP_ANALYSIS_OPTIMIZED patch; tiered pruning is always-on
• application/tests/web_main_test.py - use patch.dict(os.environ, ...) for proper env isolation

Test plan

• test_tiered_execution_optimization passes
• test_get_cre_csv passes
• test_import_from_cre_csv passes
• Full suite: 228 passed, 0 failures; 1 skipped (test_parse_row_dicts_produces_cres_and_new_standards skips when fixture file OpenCRE-AI-6-WithMitre.csv is absent, pre-existing and unrelated to this change)
• black formatting verified

[northdpole]

thanks for this pr, due to several last minute debugging changes and a brand new AI taxonomy we had to merge quickly several breaking changes, this is useful can you please resolve the conflicts so we can merge?

[shiwani42]

Yes sure, will do👍

[shiwani42]

Hi @northdpole, rebased onto main and resolved the conflicts. The scope shifted during the rebase since upstream had already removed the ENABLE_MYOPENCRE and GAP_ANALYSIS_OPTIMIZED usages, so the PR now focuses on cleaning up the dead frozen definitions and centralising the CRE_ALLOW_IMPORT gate. Updated the title and description to reflect this.

[Pa04rth]

Merged ! @shiwani42 @PRAteek-singHWY