Correct release-blocking README and startup-warning inaccuracies (closes #151)

Publishing this README would have shipped false statements about the
product. Corrects the eight items on the issue plus everything a full
sweep turned up: the Slack circuit-breaker scope, a nonexistent WAL, the
wrong config key for slack targets, six undocumented routes, the
conditional /metrics registration, wrong retention bands, wrong shutdown
mechanism, and a Quick Start that led a new contributor into a red
build.

The lockout warning now fires whenever TRUSTED_PROXIES is empty rather
than only in production, since the variable it was gated on defaults to
dev. Rate-limit keying, the limits and the TRUSTED_PROXIES default are
untouched — those belong to #150.

What /s/* actually serves was settled empirically rather than by
reading: all five of GET/HEAD/POST/PUT/DELETE return 200, pinned by
TestStaticServesEveryMethod. Restricting it is filed separately.

Independently reviewed after three prior rounds. The reviewer
re-derived all fifteen claim-table rows against the code, including
every row a previous revision had marked "correct, left alone" and got
wrong, and found zero false; then verified every route method-by-method,
all twelve environment variables, all nine entity tables, and the
package tree against git ls-files. The Quick Start was confirmed by
running it in a fresh clone.

TODO.md

@@ -25,13 +25,17 @@ password change flow (#65), policy compliance (#6), pinned lint tooling
 (#55), and fail-loud configuration parsing (#80).
 
 `next` holds the completed 1.0.0 milestone: every issue in it is closed,
-and it is verified green both by CI and by cache-defeated container
-runs. The two were only made to mean the same thing this cycle — before
-#119, a warm layer cache let the gate report success without executing
-anything, and replayed the previous build's console log so the lie
-looked like a real run. Note: TODO.md was deliberately deleted from this
-repo in f9a9569 (2026-03-01, #6); its content was folded into the README
-TODO section, which this draft reconstructs as of 2026-07-06.
+and it is verified green by cache-defeated container runs
+(`docker build --no-cache-filter=lint --no-cache-filter=builder`). The
+CI status is not independently claimed here: a superseded run is
+recorded as `skipped` and still rolls up green, so a commit status on
+`next` does not by itself evidence an executed check (#152). Before
+#119, a warm layer cache also let the gate report success without
+executing anything, and replayed the previous build's console log so
+the lie looked like a real run. Note: `TODO.md` was deliberately
+deleted from this repo in f9a9569 (2026-03-01, #6); its content was
+folded into the README TODO section, which this draft reconstructs as
+of 2026-07-06.
 
 # Next Step
 
@@ -190,7 +194,9 @@ rate-limit keys should bucket by `/64`).
     - OpenAPI specification
 - Analytics dashboard: success rates, response times, volume
 - A remember-me option at login
-- Password change and reset flow
+- Password reset flow for a forgotten password. The authenticated
+  password *change* flow already landed on `main` (#65); reset does not
+  exist
 - Later, nice to have
     - email delivery target type
     - SNS and S3 delivery targets