fix: Comprehensive v2.4.0 quality pass — 24 review findings + review agent fixes

Phase A — Critical:
- Remove dual timeout stacking in coordinator._send_to_api
- Add Gemini-specific asyncio.timeout (sync SDK via to_thread)
- Store full text in history for context; cap per-field at 32KB on disk
- Fix instance lookup to match by normalized_name
- Add Bearer/sk-/x-api-key credential sanitization patterns

Phase B — Dead code removal:
- Merge async_ask_question/async_process_question into single method
- Remove dead is_anthropic flag from coordinator and __init__
- Remove unused DEFAULT_TIMEOUT and API_TIMEOUT constants
- Remove redundant _create_history_dir calls
- Consolidate async_check_api to use provider registry

Phase C — Config flow correctness:
- Truncate name before uniqueness check (prevent post-truncation collisions)
- Add async_set_unique_id + _abort_if_unique_id_configured
- Extract shared _build_parameter_schema for ConfigFlow/OptionsFlow dedup

Phase D — UX improvements:
- Optimize history write: serialize from memory, single file write
- Show last 5 history entries in sensor attributes (was 1)
- Return actual error type in ask_question service response
- Add dedicated api_key_required error for provider/endpoint changes
- Pass config_entry to DataUpdateCoordinator (HA 2024.8+)

Phase E — Cleanup:
- Extract _apply_structured_output for OpenAI/DeepSeek dedup
- Reduce ABSOLUTE_MAX_HISTORY_SIZE to 200 with Final annotation
- Remove dead translation keys (queued, invalid_characters)
- Migrate to _attr_has_entity_name = True
- Add from __future__ import annotations to all modules
- Remove redundant api_status sensor attribute
- Add missing translation keys (last_model, last_timestamp, etc.)

Review agent fixes:
- Add archive file cleanup (max 3 archives) to prevent disk exhaustion
- Per-entry storage cap (32KB per field) for history on disk

custom_components/ha_text_ai/const.py

@@ -6,6 +6,8 @@ Constants for the HA text AI integration.
 @github: https://github.com/smkrv/ha-text-ai
 @source: https://github.com/smkrv/ha-text-ai
 """
+from __future__ import annotations
+
 from typing import Final
 from homeassistant.const import Platform
 
@@ -44,12 +46,11 @@ CONF_REQUEST_INTERVAL: Final = "request_interval"
 CONF_API_TIMEOUT: Final = "api_timeout"
 CONF_INSTANCE: Final = "instance"
 CONF_MAX_HISTORY_SIZE: Final = "max_history_size"  # Correct constant name
-CONF_IS_ANTHROPIC: Final = "is_anthropic"
 CONF_CONTEXT_MESSAGES: Final = "context_messages"
 CONF_STRUCTURED_OUTPUT: Final = "structured_output"
 CONF_JSON_SCHEMA: Final = "json_schema"
 
-ABSOLUTE_MAX_HISTORY_SIZE = 500
+ABSOLUTE_MAX_HISTORY_SIZE: Final = 200  # Hard cap; UI allows max MAX_HISTORY_SIZE (100)
 MAX_ATTRIBUTE_SIZE = 4 * 1024
 MAX_HISTORY_FILE_SIZE = 1 * 1024 * 1024
 # Default values
@@ -60,7 +61,6 @@ DEFAULT_GEMINI_MODEL: Final = "gemini-2.0-flash"
 DEFAULT_TEMPERATURE: Final = 0.1
 DEFAULT_MAX_TOKENS: Final = 1000
 DEFAULT_REQUEST_INTERVAL: Final = 1.0
-DEFAULT_TIMEOUT: Final = 30
 DEFAULT_API_TIMEOUT: Final = 30
 DEFAULT_MAX_HISTORY: Final = 50
 DEFAULT_NAME: Final = "HA Text AI"
@@ -85,7 +85,6 @@ MIN_API_TIMEOUT: Final = 5
 MAX_API_TIMEOUT: Final = 600
 
 # API constants
-API_TIMEOUT: Final = 30  # Legacy constant, use CONF_API_TIMEOUT from config
 API_RETRY_COUNT: Final = 3
 
 # Service names