feat: enhance error handling and configuration validation

- Added a global exception handler to log unhandled exceptions and return a generic 500 JSON response without exposing details to the client.
- Updated the configuration to validate the `DATABASE_URL` format, ensuring it starts with `sqlite://` or `postgresql://`, and log warnings for invalid formats.
- Introduced safe parsing for numeric environment variables (`HTTP_PORT`, `INIT_DATA_MAX_AGE_SECONDS`) with defaults on invalid values, including logging warnings for out-of-range values.
- Enhanced the duty schedule parser to enforce limits on the number of schedule rows and the length of full names and duty strings, raising appropriate errors when exceeded.
- Updated internationalization messages to include generic error responses for import failures and parsing issues, improving user experience.
- Added unit tests to verify the new error handling and configuration validation behaviors.

docs/configuration.md

@@ -5,17 +5,17 @@ All configuration is read from the environment (e.g. `.env` via python-dotenv).
 | Variable | Type / format | Default | Description |
 |----------|----------------|---------|-------------|
 | **BOT_TOKEN** | string | *(empty)* | Telegram bot token from [@BotFather](https://t.me/BotFather). Required for the bot to run; if unset, the entry point exits with a clear message. The server that serves the Mini App API must use the **same** token as the bot; otherwise initData validation returns `hash_mismatch`. |
-| **DATABASE_URL** | string (SQLAlchemy URL) | `sqlite:///data/duty_teller.db` | Database connection URL. Example: `sqlite:///data/duty_teller.db`. |
+| **DATABASE_URL** | string (SQLAlchemy URL) | `sqlite:///data/duty_teller.db` | Database connection URL. Should start with `sqlite://` or `postgresql://`; a warning is logged at startup if the format is unexpected. Example: `sqlite:///data/duty_teller.db`. |
 | **MINI_APP_BASE_URL** | string (URL, no trailing slash) | *(empty)* | Base URL of the miniapp (for documentation and CORS). Trailing slash is stripped. Example: `https://your-domain.com/app`. |
 | **HTTP_HOST** | string | `127.0.0.1` | Host to bind the HTTP server to. Use `127.0.0.1` to listen only on localhost; use `0.0.0.0` to accept connections from all interfaces (e.g. when behind a reverse proxy on another machine). |
-| **HTTP_PORT** | integer | `8080` | Port for the HTTP server (FastAPI + static webapp). |
+| **HTTP_PORT** | integer (1–65535) | `8080` | Port for the HTTP server (FastAPI + static webapp). Invalid or out-of-range values are clamped; non-numeric values fall back to 8080. |
 | **ALLOWED_USERNAMES** | comma-separated list | *(empty)* | **Not used for access.** Kept for reference only. Access to the miniapp is controlled by **roles in the DB** (assigned by an admin via `/set_role`). |
 | **ADMIN_USERNAMES** | comma-separated list | *(empty)* | Telegram usernames treated as **admin fallback** when the user has **no role in the DB**. If a user has a role in the DB, only that role applies. Example: `admin1,admin2`. |
 | **ALLOWED_PHONES** | comma-separated list | *(empty)* | **Not used for access.** Kept for reference only. |
 | **ADMIN_PHONES** | comma-separated list | *(empty)* | Phones treated as **admin fallback** when the user has **no role in the DB** (user sets phone via `/set_phone`). Comparison uses digits only. Example: `+7 999 123-45-67`. |
-| **MINI_APP_SKIP_AUTH** | `1`, `true`, or `yes` | *(unset)* | If set, `/api/duties` and `/api/calendar-events` are allowed without Telegram initData. **Dev only — never use in production.** |
-| **INIT_DATA_MAX_AGE_SECONDS** | integer | `0` | Reject Telegram initData older than this many seconds. `0` = disabled. Example: `86400` for 24 hours. |
-| **CORS_ORIGINS** | comma-separated list | `*` | Allowed origins for CORS. Leave unset or set to `*` for allow-all. Example: `https://your-domain.com`. |
+| **MINI_APP_SKIP_AUTH** | `1`, `true`, or `yes` | *(unset)* | If set, `/api/duties` and `/api/calendar-events` are allowed without Telegram initData. **Dev only — never use in production.** The process exits with an error if this is set and **HTTP_HOST** is not localhost (127.0.0.1). |
+| **INIT_DATA_MAX_AGE_SECONDS** | integer (≥ 0) | `0` | Reject Telegram initData older than this many seconds. `0` = disabled. Invalid values fall back to 0. Example: `86400` for 24 hours. |
+| **CORS_ORIGINS** | comma-separated list | `*` | Allowed origins for CORS. Leave unset or set to `*` for allow-all. **In production**, set an explicit list (e.g. `https://your-domain.com`) instead of `*` to avoid allowing arbitrary origins. Example: `https://your-domain.com`. |
 | **EXTERNAL_CALENDAR_ICS_URL** | string (URL) | *(empty)* | URL of a public ICS calendar (e.g. holidays). If set, those days are highlighted on the duty grid; users can tap "i" on a cell to see the event summary. Empty = no external calendar. |
 | **DUTY_DISPLAY_TZ** | string (timezone name) | `Europe/Moscow` | Timezone for the pinned duty message in groups. Example: `Europe/Moscow`, `UTC`. |
 | **DUTY_PIN_NOTIFY** | `0`, `false`, or `no` to disable | `1` (enabled) | When the pinned duty message is updated on schedule, the bot sends a new message, unpins the old one and pins the new one. If enabled, pinning the new message sends a Telegram notification (“Bot pinned a message”). Set to `0`, `false`, or `no` to pin without notification. The first pin (e.g. when the bot is added to the group or on `/pin_duty`) is always silent. |