feat: revamp analytics dashboards and harden database migrations

Add dashboard and overview analytics, health monitoring, provider expense tracking, and announcement updates across the gateway and frontend.

Keep schema migrations free of historical backfills while preserving automatic backfill execution. Bound migration deadlines, run schema preparation before Compose replacement, and anonymize deleted dashboard users.

Include the current documentation cleanup and regression coverage.

crates/aether-data/runtime/schema/generated/postgres/baseline/006_usage.sql

@@ -99,7 +99,11 @@ CREATE TABLE IF NOT EXISTS public.usage (
     wallet_gift_balance_after double precision,
     finalized_at bigint,
     created_at_unix_ms bigint DEFAULT 0 NOT NULL,
-    updated_at_unix_secs bigint DEFAULT 0 NOT NULL
+    updated_at_unix_secs bigint DEFAULT 0 NOT NULL,
+    failure_origin text,
+    failure_stage text,
+    failure_reason text,
+    failure_schema_version integer
 );
 
 ALTER TABLE ONLY public.usage ADD CONSTRAINT usage_pkey PRIMARY KEY (request_id);
@@ -204,6 +208,14 @@ CREATE INDEX IF NOT EXISTS ix_usage_counter_deltas_request_kind ON public.usage_
 CREATE TABLE IF NOT EXISTS public.usage_settlement_snapshots (
     request_id character varying(128) NOT NULL,
     billing_status character varying(64) NOT NULL,
+    quota_covered_amount_usd numeric(20,8),
+    wallet_consumed_amount_usd numeric(20,8),
+    wallet_debit_amount_usd numeric(20,8),
+    wallet_recharge_debit_usd numeric(20,8),
+    wallet_gift_debit_usd numeric(20,8),
+    wallet_overdraft_usd numeric(20,8),
+    allocation_schema_version integer,
+    allocation_status text,
     wallet_id character varying(64),
     wallet_balance_before double precision,
     wallet_balance_after double precision,