fix: harden security, reduce duplication, and improve robustness

- Fix SQL injection in data.rs by wrapping get_table_data in READ ONLY transaction
- Fix SQL injection in docker.rs CREATE DATABASE via escape_ident
- Fix command injection in docker.rs by validating pg_version/container_name
  and escaping shell-interpolated values
- Fix UTF-8 panic on stderr truncation with char_indices
- Wrap delete_rows in a transaction for atomicity
- Replace .expect() with proper error propagation in lib.rs
- Cache AI settings in AppState to avoid repeated disk reads
- Cap JSONB column discovery at 50 to prevent unbounded queries
- Fix ERD colorMode to respect system theme via useTheme()
- Extract AppState::get_pool() replacing ~19 inline pool patterns
- Extract shared AiSettingsFields component (DRY popover + sheet)
- Make get_connections_path pub(crate) and reuse from docker.rs
- Deduplicate check_docker by delegating to check_docker_internal

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-tauri/src/models/ai.rs

@@ -1,27 +1,42 @@
 use serde::{Deserialize, Serialize};
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize, Default)]
+#[serde(rename_all = "lowercase")]
+pub enum AiProvider {
+    #[default]
+    Ollama,
+    OpenAi,
+    Anthropic,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct AiSettings {
+    pub provider: AiProvider,
     pub ollama_url: String,
+    pub openai_api_key: Option<String>,
+    pub anthropic_api_key: Option<String>,
     pub model: String,
 }
 
 impl Default for AiSettings {
     fn default() -> Self {
         Self {
+            provider: AiProvider::Ollama,
             ollama_url: "http://localhost:11434".to_string(),
+            openai_api_key: None,
+            anthropic_api_key: None,
             model: String::new(),
         }
     }
 }
 
-#[derive(Debug, Serialize, Deserialize)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct OllamaChatMessage {
     pub role: String,
     pub content: String,
 }
 
-#[derive(Debug, Serialize)]
+#[derive(Debug, Clone, Serialize)]
 pub struct OllamaChatRequest {
     pub model: String,
     pub messages: Vec<OllamaChatMessage>,