Refactor database connection handling and streamline show commands

[OutOfBedlam]

This pull request refactors database connection handling and SQL execution across the codebase to standardize on Go's database/sql package and improve consistency, reliability, and maintainability. It replaces custom connection interfaces with *sql.Conn, updates function signatures, and refactors SQL execution logic in server handlers and TQL modules. Additionally, it modernizes error handling and improves test diagnostics.

Database connection and execution refactoring:

• Replaced custom api.Conn usage with *sql.Conn from the standard library throughout the server and TQL modules, updating function signatures and connection acquisition logic accordingly. (mods/server/http.go, mods/server/http_query.go, mods/server/http_write.go, mods/tql/fm_dbsink.go, mods/tql/fm_dbsrc.go) [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14]

• Refactored SQL execution paths to use context-aware methods (ExecContext, QueryRowContext) and improved error propagation and handling. (mods/server/http_write.go, mods/tql/fm_dbsink.go, mods/tql/fm_dbsrc.go) [1] [2] [3] [4]

Server handler improvements:

• Updated HTTP handlers to use the new connection methods, added stricter authorization checks for license installation, and improved resource cleanup with proper defer usage. (mods/server/http.go) [1] [2] [3]

• Changed table listing logic to pass errors directly and improved callback signatures for clarity. (mods/server/http_query.go)

TQL module enhancements:

• Simplified and clarified TQL node implementations by removing unnecessary provider indirection, ensuring connections are acquired and closed consistently, and updating SQL sink logic to use the new connection style. (mods/tql/fm_dbsink.go, mods/tql/fm_dbsrc.go) [1] [2] [3] [4]

Testing and dependency updates:

• Improved test diagnostics by including response bodies in assertion messages for easier debugging. (mods/server/http_test.go)

• Updated dependency version for github.com/machbase/neo-client in go.mod.

[codecov]

Codecov Report

❌ Patch coverage is 69.71154% with 126 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.92%. Comparing base (0c754c5) to head (258c64c).

Files with missing lines	Patch %	Lines
spi/do.go	50.00%	16 Missing and 8 partials ⚠️
spi/database.go	25.92%	19 Missing and 1 partial ⚠️
mods/tql/fm_dbsink.go	35.71%	7 Missing and 11 partials ⚠️
spi/show.go	94.02%	4 Missing and 7 partials ⚠️
mods/server/http_query.go	54.54%	4 Missing and 6 partials ⚠️
spi/watch.go	56.52%	8 Missing and 2 partials ⚠️
mods/server/http_write.go	50.00%	4 Missing and 5 partials ⚠️
mods/tql/fm_dbsrc.go	78.04%	5 Missing and 4 partials ⚠️
mods/server/http.go	38.46%	8 Missing ⚠️
mods/server/mqtt_write.go	45.45%	3 Missing and 3 partials ⚠️
... and 1 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #449      +/-   ##
==========================================
- Coverage   65.95%   65.92%   -0.04%     
==========================================
  Files         345      343       -2     
  Lines       70557    70286     -271     
==========================================
- Hits        46533    46333     -200     
+ Misses      19087    18997      -90     
- Partials     4937     4956      +19     

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