feat: add personalization service with EnglishV3-only reranking

- Add new personalization module with Cohere integration
- Implement rerank_search_results method using EnglishV3 model
- Remove fallback logic to EnglishV2 for simplified behavior
- Add comprehensive error handling and logging
- Include unit tests for service behavior
- Update search route to support personalization feature

Cargo.lock

@@ -1194,6 +1194,21 @@ version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f46ad14479a25103f283c0f10005961cf086d8dc42205bb44c46ac563475dca6"
 
+[[package]]
+name = "cohere-rust"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d8b553b385b0f2562138baea705b5707335314f8e91a58e7d1a03c3a6c332423"
+dependencies = [
+ "bytes",
+ "reqwest",
+ "serde",
+ "serde_json",
+ "strum_macros 0.26.4",
+ "thiserror 1.0.69",
+ "tokio",
+]
+
 [[package]]
 name = "color-spantrace"
 version = "0.3.0"
@@ -3445,7 +3460,7 @@ dependencies = [
  "serde_json",
  "serde_yaml",
  "strum",
- "strum_macros",
+ "strum_macros 0.27.1",
  "unicode-blocks",
  "unicode-normalization",
  "unicode-segmentation",
@@ -3753,6 +3768,7 @@ dependencies = [
  "bytes",
  "cargo_toml",
  "clap",
+ "cohere-rust",
  "crossbeam-channel",
  "deserr",
  "dump",
@@ -5822,7 +5838,20 @@ version = "0.27.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f64def088c51c9510a8579e3c5d67c65349dcf755e5479ad3d010aa6454e2c32"
 dependencies = [
- "strum_macros",
+ "strum_macros 0.27.1",
+]
+
+[[package]]
+name = "strum_macros"
+version = "0.26.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c6bee85a5a24955dc440386795aa378cd9cf82acd5f764469152d2270e581be"
+dependencies = [
+ "heck",
+ "proc-macro2",
+ "quote",
+ "rustversion",
+ "syn 2.0.101",
 ]
 
 [[package]]