[bthome] Use StaticVector with compile-time sizes

Switch from FixedVector (runtime-sized, heap allocated) to StaticVector
(compile-time sized, stack allocated) for better memory efficiency:

**Changes:**
- Replace FixedVector with StaticVector in bthome.h
- Use cg.add_define to set sizes at compile time before creating component
- Remove runtime init() calls (StaticVector doesn't need them)
- Add default defines to esphome/core/defines.h for static analysis

**Benefits:**
- All memory allocated on stack at compile time
- Zero runtime allocation overhead
- Better for embedded systems with limited heap
- StaticVector allocates all N slots upfront (no dynamic growth)

**Defines added:**
- BTHOME_MAX_MEASUREMENTS: Max number of sensor measurements
- BTHOME_MAX_BINARY_MEASUREMENTS: Max number of binary sensor measurements
- BTHOME_MAX_ADV_PACKETS: Max advertisement packets for cycling

Sizes are calculated from YAML config and set via cg.add_define before
component instantiation, ensuring compile-time type safety.

esphome/components/bthome/__init__.py

@@ -172,6 +172,16 @@ FINAL_VALIDATE_SCHEMA = esp32_ble.validate_variant
 
 
 async def to_code(config):
+    # Calculate sizes for StaticVector compile-time allocation
+    num_sensors = max(1, len(config.get(CONF_SENSORS, [])))
+    num_binary_sensors = max(1, len(config.get(CONF_BINARY_SENSORS, [])))
+    max_packets = max(1, num_sensors + num_binary_sensors)
+
+    # Add defines for compile-time sizes (must be before new_Pvariable)
+    cg.add_define("BTHOME_MAX_MEASUREMENTS", num_sensors)
+    cg.add_define("BTHOME_MAX_BINARY_MEASUREMENTS", num_binary_sensors)
+    cg.add_define("BTHOME_MAX_ADV_PACKETS", max_packets)
+
     var = cg.new_Pvariable(config[CONF_ID])
 
     parent = await cg.get_variable(config[esp32_ble.CONF_BLE_ID])
@@ -182,17 +192,6 @@ async def to_code(config):
     cg.add(var.set_max_interval(config[CONF_MAX_INTERVAL]))
     cg.add(var.set_tx_power(config[CONF_TX_POWER]))
 
-    # Initialize FixedVectors with proper sizes
-    num_sensors = len(config.get(CONF_SENSORS, []))
-    num_binary_sensors = len(config.get(CONF_BINARY_SENSORS, []))
-    max_packets = max(1, num_sensors + num_binary_sensors)
-
-    # Initialize the measurements and binary_measurements FixedVectors
-    cg.add(cg.RawExpression(f"{var}->measurements_.init({num_sensors})"))
-    cg.add(cg.RawExpression(f"{var}->binary_measurements_.init({num_binary_sensors})"))
-    cg.add(cg.RawExpression(f"{var}->adv_packets_.init({max_packets})"))
-    cg.add(cg.RawExpression(f"{var}->adv_packet_sizes_.init({max_packets})"))
-
     if CONF_ENCRYPTION_KEY in config:
         key = config[CONF_ENCRYPTION_KEY]
         key_bytes = [cg.RawExpression(f"0x{key[i:i+2]}") for i in range(0, len(key), 2)]

esphome/components/bthome/bthome.h

@@ -57,8 +57,8 @@ class BTHome : public Component, public GAPEventHandler, public Parented<ESP32BL
   bool encrypt_payload_(const uint8_t *plaintext, size_t plaintext_len, uint8_t *ciphertext, size_t *ciphertext_len);
   void trigger_immediate_advertising_(uint8_t measurement_index, bool is_binary);
 
-  FixedVector<SensorMeasurement> measurements_;
+  StaticVector<SensorMeasurement, BTHOME_MAX_MEASUREMENTS> measurements_;
-  FixedVector<BinarySensorMeasurement> binary_measurements_;
+  StaticVector<BinarySensorMeasurement, BTHOME_MAX_BINARY_MEASUREMENTS> binary_measurements_;
 
   uint16_t min_interval_{};
   uint16_t max_interval_{};
@@ -72,8 +72,8 @@ class BTHome : public Component, public GAPEventHandler, public Parented<ESP32BL
   uint32_t counter_{0};
 
   // Advertisement cycling support
-  FixedVector<std::unique_ptr<uint8_t[]>> adv_packets_;  // Multiple advertisement packets
+  StaticVector<std::unique_ptr<uint8_t[]>, BTHOME_MAX_ADV_PACKETS> adv_packets_;  // Multiple advertisement packets
-  FixedVector<uint16_t> adv_packet_sizes_;               // Size of each packet
+  StaticVector<uint16_t, BTHOME_MAX_ADV_PACKETS> adv_packet_sizes_;               // Size of each packet
   uint8_t current_packet_index_{0};
   bool data_changed_{true};
   bool immediate_advertising_pending_{false};

esphome/core/defines.h

@@ -176,6 +176,9 @@
 #define USE_ESP32_BLE_SERVER
 #define USE_ESP32_BLE_UUID
 #define USE_ESP32_BLE_ADVERTISING
+#define BTHOME_MAX_MEASUREMENTS 8
+#define BTHOME_MAX_BINARY_MEASUREMENTS 8
+#define BTHOME_MAX_ADV_PACKETS 16
 #define USE_ESP32_BLE_SERVER_SET_VALUE_ACTION
 #define USE_ESP32_BLE_SERVER_DESCRIPTOR_SET_VALUE_ACTION
 #define USE_ESP32_BLE_SERVER_NOTIFY_ACTION