feat: serve the day, its index, the timeline and life events

Replace the day, timeline and life-event stubs with their implementations
(#613) and drop the not-implemented helper, its error code and its OpenAPI
response with the last stub.

loadDay reads one local day for every reader: the readings live inside the
record's own day window (never the UTC rollups), through the canonical-source
engine the mood sheet already uses (resolveDayReadings in linked-context.ts),
with the person's usual range over the 30 days before; the record sections
from their own tables, each in the storage form it speaks (an instant in the
local window, a date string with its own zone, a calendar date). A switched-off
module's section is not read; a section the grant does not cover is named
not_shared and not read.

The day, the day index and the new visit preparation (GET /api/day/notable)
are admitted on the readings and narrowed per section through
actingDomainVisibility, so a scoped grant sees exactly its sections. The
timeline and its readiness stay whole-record reads and narrow their lanes the
same way.

Notable days are deterministic keys: a three-month high or low with history
behind it, a first reading, and in the visit preparation a regular reading
that stopped. The timeline lays out spans and points from the owning tables,
standing items without a date, and series by zoom: months from the rollup
tier inside its five-year window and from one cached live query before it.
The readiness inventory rates each lane with one link per gap.

Life events are created, edited and soft-deleted as MANAGE verbs with audit
rows, encrypted at rest, and join the sharing guard and the handler matrix.
get_day reads a day for the Coach and the MCP endpoint without life events,
notes or document names; its step carries the date it read.

src/lib/openapi/error-codes.ts

@@ -118,6 +118,7 @@ export const ERROR_CODE_CATALOGUE: Readonly<Record<string, readonly string[]>> =
     ],
     "cycle-prefs": ["cycle-prefs.body.invalid_json", "cycle-prefs.invalid"],
     "disable-coach": ["disable-coach.body.invalid_json"],
+    day: ["day.invalid"],
     demo: ["demo.readOnly"],
     documents: [
       "documents.chat.conversationNotFound",
@@ -230,6 +231,7 @@ export const ERROR_CODE_CATALOGUE: Readonly<Record<string, readonly string[]>> =
       "labs.update.referenceRangeInvalid",
       "labs.update.sourceReferenceRangeInvalid",
     ],
+    life_event: ["life_event.invalid", "life_event.not_found"],
     managed_profile: [
       "managed_profile.guardian.duplicate",
       "managed_profile.guardian.managed_invitee",
@@ -380,6 +382,7 @@ export const ERROR_CODE_CATALOGUE: Readonly<Record<string, readonly string[]>> =
       "symptoms.event.notFound",
       "symptoms.invalid",
     ],
+    timeline: ["timeline.invalid"],
     tokens: [
       "tokens.documents.ceiling_reached",
       "tokens.measurements.ceiling_reached",
@@ -423,7 +426,6 @@ export const ERROR_CODE_CATALOGUE: Readonly<Record<string, readonly string[]>> =
       "modules_conflict",
       "mood_tag_layout_conflict",
       "not_configured",
-      "not_implemented",
       "notification_prefs_conflict",
       "oidc_only",
       "private_origin_not_approved",