refactor: migrate monolithic crate to Cargo Workspace with Clean Architecture

Transform the single binary crate into a 9-crate workspace monorepo:

- Root Cargo.toml as [workspace] manager with resolver = "2"
- zesdex-entities: Domain entity types (session, settings, store, message, etc.)
- zesdex-utils: Pure utility functions (error, logger, pagination, slug, clipboard)
- zesdex-dto: Data Transfer Objects for LLM provider API communication
- zesdex-ipc: Unix-socket IPC layer (client/server/framing/protocol)
- zesdex-iam: Identity & Access Management (Clean Architecture: domain/application/infrastructure)
- zesdex-cms: Content Management (Clean Architecture: domain/application/infrastructure)
- zesdex-middleware: HTTP middleware (Auth, CORS, Rate Limiting)
- zesdex-libs: Composition root (AppContext, DB init, JWT, Argon2)
- zesdex-backend: Main binary entry point + seed/migrate binaries
- DevOps: Dockerfile, docker-compose, Nix (flake/shell/default), CI/CD updates
- Remove dead root src/ and src-misc/ directories

All crate re-exports maintain backward compatibility with original
crate::model::*, crate::dto::*, crate::ipc::* module paths.
Feature crates enforce strict layer separation: domain -> application
-> infrastructure with generic trait-based dependency injection.

Cargo.toml

@@ -1,11 +1,23 @@
-[package]
-name = "zesdex"
-version = "1.14.0"
+[workspace]
+resolver = "2"
+members = [
+    "crates/zesdex-entities",
+    "crates/zesdex-utils",
+    "crates/zesdex-dto",
+    "crates/zesdex-ipc",
+    "crates/zesdex-iam",
+    "crates/zesdex-cms",
+    "crates/zesdex-middleware",
+    "crates/zesdex-libs",
+    "crates/zesdex-backend",
+]
+
+[workspace.package]
+version = "1.13.0"
 edition = "2021"
 authors = ["asepharyana <superaseph@gmail.com>"]
 
-# Treat all warnings as errors, set strict clippy levels
-[lints.rust]
+[workspace.lints.rust]
 unused = "deny"
 dead_code = "deny"
 unreachable_code = "deny"
@@ -17,49 +29,55 @@ deprecated = "deny"
 trivial_casts = "deny"
 trivial_numeric_casts = "deny"
 
-[lints.clippy]
+[workspace.lints.clippy]
 all = { level = "warn", priority = -1 }
 pedantic = { level = "warn", priority = -2 }
 
-[dependencies]
-ratatui = "0.30.2"
-crossterm = "0.29"
-tokio = { version = "1", features = ["rt-multi-thread", "macros", "sync", "time", "net", "io-util", "signal"] }
-reqwest = { version = "0.13", features = ["json", "stream", "blocking", "native-tls-vendored", "form"] }
-dom_smoothie = "0.18.0"
-fast_html2md = "0.0.62"
-scraper = "0.27.0"
-url = "2"
-percent-encoding = "2"
+[workspace.dependencies]
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 serde_yaml_ng = "0.10"
-anyhow = "1"
-include_dir = "0.7"
+chrono = { version = "0.4", features = ["serde"] }
 uuid = { version = "1", features = ["v4", "v5"] }
-dirs = "6"
-futures-util = "0.3"
-pulldown-cmark = { version = "0.13", default-features = false }
-similar = "3"
-syntect = { version = "5", default-features = false, features = ["default-fancy"] }
+anyhow = "1"
+tokio = { version = "1", features = ["rt-multi-thread", "macros", "sync", "time", "net", "io-util", "signal"] }
+tracing = "0.1"
+tracing-subscriber = { version = "0.3", features = ["env-filter"] }
+reqwest = { version = "0.13", features = ["json", "stream", "blocking", "native-tls-vendored", "form"] }
+ratatui = "0.30.2"
+crossterm = "0.29"
 rusqlite = { version = "0.40", features = ["bundled"] }
-ignore = "0.4"
-regex = "1"
-globset = "0.4"
-nucleo-matcher = "0.3"
-infer = "0.19"
+thiserror = "1"
 base64 = "0.22"
 sha2 = "0.11"
 hex = "0.4"
 libc = "0.2"
+dirs = "6"
+regex = "1"
+globset = "0.4"
+ignore = "0.4"
+nucleo-matcher = "0.3"
+futures-util = "0.3"
 rmcp = { version = "2.2", default-features = false, features = ["client", "transport-child-process", "transport-streamable-http-client-reqwest", "macros"] }
-tracing = "0.1"
-chrono = { version = "0.4", features = ["serde"] }
-tracing-subscriber = { version = "0.3", features = ["env-filter"] }
-webbrowser = "1"
 lsp-types = "0.97"
 tiktoken-rs = "0.12"
+similar = "3"
+syntect = { version = "5", default-features = false, features = ["default-fancy"] }
+pulldown-cmark = { version = "0.13", default-features = false }
+infer = "0.19"
+webbrowser = "1"
+url = "2"
+percent-encoding = "2"
+dom_smoothie = "0.18.0"
+fast_html2md = "0.0.62"
+scraper = "0.27.0"
+include_dir = "0.7"
+axum = { version = "0.8", features = ["macros"] }
+tower = "0.5"
+tower-http = { version = "0.6", features = ["cors", "limit"] }
+argon2 = "0.5"
+jsonwebtoken = "9"
 
-[[bin]]
-name = "zesdex"
-path = "src/main.rs"
+zesdex-entities = { path = "crates/zesdex-entities" }
+zesdex-utils = { path = "crates/zesdex-utils" }
+zesdex-dto = { path = "crates/zesdex-dto" }