test(coverage): enforce API and app floors

Measure untouched mobile source, add regression coverage for native media paths and account operations, and enforce ratcheting API and mobile thresholds in required CI checks.

docs/testing/strategy.md

@@ -12,6 +12,16 @@ is proved through the real stack.
   already-running local stack.
 - `verify`: full plus E2E; this is the pre-PR target.
 
+The required CI checks also run instrumented coverage for the API and mobile
+workspaces. Mobile coverage includes every TypeScript file under `app` and
+`src`, including files no test imports. The committed thresholds are ratchets,
+not targets: raise them as coverage improves, and never narrow the collected
+source set to make a percentage pass.
+
+- API unit floor: 30% statements/lines, 60% branches, 40% functions.
+- API PostgreSQL integration floor: 55% statements/lines, 65% branches/functions.
+- Mobile floor: 23% statements/lines, 17% branches, 21% functions.
+
 CI runs deterministic checks on every pull request and on pushes to `staging`
 and `main`. The backend integration job provisions disposable PostgreSQL and
 refuses non-loopback database URLs. User-facing browser/native acceptance remains