feat(bot): add multi-household reminder delivery

docs/specs/HOUSEBOT-075-multi-household-reminder-delivery.md

@@ -0,0 +1,53 @@
+# HOUSEBOT-075 Multi-Household Reminder Delivery
+
+## Goal
+
+Replace the current reminder placeholder path with a real multi-household reminder dispatcher.
+
+## Problem
+
+Current reminder jobs only claim a dedupe key and return `messageText`. They do not send any Telegram message. They also require a single global `HOUSEHOLD_ID`, which is incompatible with the bot's DB-backed multi-household model.
+
+## Target behavior
+
+- Scheduler endpoint accepts `utilities`, `rent-warning`, or `rent-due`
+- For the target billing period, the bot resolves all configured household reminder targets from the database
+- A household reminder target uses:
+  - bound `reminders` topic if present
+  - otherwise the household chat itself
+- For each target household, the bot:
+  - builds deterministic reminder text
+  - claims dedupe for `(householdId, period, reminderType)`
+  - posts the message to Telegram only when the claim succeeds
+- Dry-run returns the planned dispatches without posting
+
+## Delivery model
+
+- Scheduler route remains a single endpoint per reminder type
+- One request fan-outs across all reminder-enabled households
+- Logs include an entry per household outcome
+
+## Data source
+
+Household config comes from `HouseholdConfigurationRepository`:
+
+- household chat binding is required
+- reminder topic binding is optional
+
+## Runtime contract
+
+Reminder jobs require:
+
+- `DATABASE_URL`
+- one scheduler auth mechanism (`SCHEDULER_SHARED_SECRET` or allowed OIDC service accounts)
+
+Reminder jobs must not require:
+
+- `HOUSEHOLD_ID`
+- group/topic reminder env vars
+
+## Follow-ups
+
+- per-household reminder settings
+- localized reminder copy using persisted household/member locale
+- scheduler fan-out observability metrics