Remove SQLite: use in-memory cache instead

PROJECT_PLAN.md

@@ -30,11 +30,11 @@ A lightweight Go service that:
 ## Tech Stack
 
 - **Language**: Go
-- **Database**: SQLite (local cache)
 - **Source DB**: Gitea MySQL (read-only, same docker network)
 - **HTTP**: Standard library `net/http`
 - **Deployment**: Docker + Docker Compose on vps.git
 - **API Key**: Rotates every 10 minutes, stored in Docker volume at `/data/api-key`
+- **Cache**: In-memory map (repo_id → Repo), refreshed every 5h + webhook updates
 
 ## Authentication
 
@@ -97,16 +97,20 @@ Returns `{"status": "ok"}`.
 
 ## Data Model
 
-### SQLite cache table: `repos`
+### In-memory cache: `map[int64]*Repo`
 
-| Column       | Type    | Notes                        |
-|--------------|---------|------------------------------|
-| id           | INTEGER | Gitea repo ID (primary key)  |
-| name         | TEXT    |                              |
-| owner        | TEXT    | Gitea username of owner      |
-| is_private   | INTEGER | 0 or 1                       |
-| url          | TEXT    | Full .git HTTPS URL          |
-| updated_at   | INTEGER | Unix timestamp of last sync   |
+```go
+type Repo struct {
+    ID        int64
+    Name      string
+    Owner     string
+    IsPrivate bool
+    URL       string
+}
+```
+
+Cached in a `sync.RWMutex`-protected map keyed by Gitea repo ID.
+Refreshed on startup, every 5 hours, and on webhook events.
 
 ## Configuration
 
@@ -118,8 +122,6 @@ Environment variables:
 | `DB_USER`     | `root`  | MySQL username               |
 | `DB_PASS`     | —       | MySQL password               |
 | `DB_NAME`     | `giteadb` | MySQL database name        |
-| `SQLITE_PATH` | `/data/cache.db` | SQLite file path              |
-| `API_KEY_FILE` | `/data/api-key` | Path for rotating api-key       |
 | `WEBHOOK_SECRET` | —      | Gitea webhook secret token       |
 | `PORT`        | `8080`  | HTTP listen port             |
 
@@ -150,11 +152,9 @@ services:
       DB_USER: root
       DB_PASS: ${MYSQL_ROOT_PASSWORD}
       DB_NAME: giteadb
-      SQLITE_PATH: /data/cache.db
       WEBHOOK_SECRET: ${GITEA_WEBHOOK_SECRET}
       PORT: 8080
     volumes:
-      - ./gitea-custom-api/data:/data
       - ./gitea-custom-api/api-key:/data/api-key
     networks:
       - git-network